Jack n.
 1. A familiar nickname of, or substitute for, John.
    You are John Rugby, and you are Jack Rugby.   --Shak.
 2. An impertinent or silly fellow; a simpleton; a boor; a clown; also, a servant; a rustic. “Jack fool.”
 Since every Jack became a gentleman,
 There 's many a gentle person made a Jack.   --Shak.
 3. A popular colloquial name for a sailor; -- called also Jack tar, and Jack afloat.
 4. A mechanical contrivance, an auxiliary machine, or a subordinate part of a machine, rendering convenient service, and often supplying the place of a boy or attendant who was commonly called Jack; as: (a) A device to pull off boots. (b) A sawhorse or sawbuck. (c) A machine or contrivance for turning a spit; a smoke jack, or kitchen jack. (b) Mining A wooden wedge for separating rocks rent by blasting. (e) Knitting Machine A lever for depressing the sinkers which push the loops down on the needles. (f) Warping Machine A grating to separate and guide the threads; a heck box. (g) Spinning A machine for twisting the sliver as it leaves the carding machine. (h) A compact, portable machine for planing metal. (i) A machine for slicking or pebbling leather. (k) A system of gearing driven by a horse power, for multiplying speed. (l) A hood or other device placed over a chimney or vent pipe, to prevent a back draught. (m) In the harpsichord, an intermediate piece communicating the action of the key to the quill; -- called also hopper. (n) In hunting, the pan or frame holding the fuel of the torch used to attract game at night; also, the light itself.  --C. Hallock.
 5. A portable machine variously constructed, for exerting great pressure, or lifting or moving a heavy body such as an automobile through a small distance. It consists of a lever, screw, rack and pinion, hydraulic press, or any simple combination of mechanical powers, working in a compact pedestal or support and operated by a lever, crank, capstan bar, etc. The name is often given to a jackscrew, which is a kind of jack.
 6. The small bowl used as a mark in the game of bowls.
    Like an uninstructed bowler who thinks to attain the jack by delivering his bowl straight forward upon it.   --Sir W. Scott.
 7. The male of certain animals, as of the ass.
 8. Zool. (a) A young pike; a pickerel. (b) The jurel. (c) A large, California rock fish (Sebastodes paucispinus); -- called also boccaccio, and mérou. (d) The wall-eyed pike.
 9. A drinking measure holding half a pint; also, one holding a quarter of a pint. [Prov. Eng.]
 10. Naut. (a) A flag, containing only the union, without the fly, usually hoisted on a jack staff at the bowsprit cap; -- called also union jack. The American jack is a small blue flag, with a star for each State. (b) A bar of iron athwart ships at a topgallant masthead, to support a royal mast, and give spread to the royal shrouds; -- called also jack crosstree.
 11. The knave of a suit of playing cards.
 Note: ☞ Jack is used adjectively in various senses. It sometimes designates something cut short or diminished in size; as, a jack timber; a jack rafter; a jack arch, etc.
 Jack arch, an arch of the thickness of one brick.
 Jack back Brewing & Malt Vinegar Manuf., a cistern which receives the wort. See under 1st Back.
 Jack block Naut., a block fixed in the topgallant or royal rigging, used for raising and lowering light masts and spars.
 Jack boots, boots reaching above the knee; -- worn in the 17 century by soldiers; afterwards by fishermen, etc.
 Jack crosstree. Naut. See 10, b, above.
 Jack curlew Zool., the whimbrel.
 Jack frame. Cotton Spinning See 4 (g), above.
 Jack Frost, frost or cold weather personified as a mischievous person.
 Jack hare, a male hare. --Cowper.
 Jack lamp, a lamp for still hunting and camp use. See def. 4 (n.), above.
 Jack plane, a joiner's plane used for coarse work.
 Jack post, one of the posts which support the crank shaft of a deep-well-boring apparatus.
 Jack pot Poker Playing, the name given to the stakes, contributions to which are made by each player successively, till such a hand is turned as shall take the “pot,” which is the sum total of all the bets.  See also jackpot.
 Jack rabbit Zool., any one of several species of large American hares, having very large ears and long legs. The California species (Lepus Californicus), and that of Texas and New Mexico (Lepus callotis), have the tail black above, and the ears black at the tip. They do not become white in winter. The more northern prairie hare (Lepus campestris) has the upper side of the tail white, and in winter its fur becomes nearly white.
 Jack rafter Arch., in England, one of the shorter rafters used in constructing a hip or valley roof; in the United States, any secondary roof timber, as the common rafters resting on purlins in a trussed roof; also, one of the pieces simulating extended rafters, used under the eaves in some styles of building.
 Jack salmon Zool., the wall-eyed pike, or glasseye.
 Jack sauce, an impudent fellow. [Colloq. & Obs.]
 Jack shaft Mach., the first intermediate shaft, in a factory or mill, which receives power, through belts or gearing, from a prime mover, and transmits it, by the same means, to other intermediate shafts or to a line shaft.
 Jack sinker Knitting Mach., a thin iron plate operated by the jack to depress the loop of thread between two needles.
 Jack snipe. Zool. See in the Vocabulary.
 Jack staff Naut., a staff fixed on the bowsprit cap, upon which the jack is hoisted.
 Jack timber Arch., any timber, as a rafter, rib, or studding, which, being intercepted, is shorter than the others.
 Jack towel, a towel hung on a roller for common use.
 Jack truss Arch., in a hip roof, a minor truss used where the roof has not its full section.
 Jack tree. Bot. See 1st Jack, n.
 Jack yard Naut., a short spar to extend a topsail beyond the gaff.
 Blue jack, blue vitriol; sulphate of copper.
 Hydraulic jack, a jack used for lifting, pulling, or forcing, consisting of a compact portable hydrostatic press, with its pump and a reservoir containing a supply of liquid, as oil.
 Jack-at-a-pinch. (a) One called upon to take the place of another in an emergency. (b) An itinerant parson who conducts an occasional service for a fee.
 Jack-at-all-trades, one who can turn his hand to any kind of work.
 Jack-by-the-hedge Bot., a plant of the genus Erysimum (Erysimum alliaria, or Alliaria officinalis), which grows under hedges. It bears a white flower and has a taste not unlike garlic. Called also, in England, sauce-alone. --Eng. Cyc.
 Jack-in-office, an insolent fellow in authority. --Wolcott.
 Jack-in-the-bush Bot., a tropical shrub with red fruit (Cordia Cylindrostachya).
 Jack-in-the-green, a chimney sweep inclosed in a framework of boughs, carried in Mayday processions.
 Jack-of-the-buttery Bot., the stonecrop (Sedum acre).
 Jack-of-the-clock, a figure, usually of a man, on old clocks, which struck the time on the bell.
 Jack-on-both-sides, one who is or tries to be neutral.
 Jack-out-of-office, one who has been in office and is turned out. --Shak.
 Jack the Giant Killer, the hero of a well-known nursery story.
 Yellow Jack Naut., the yellow fever; also, the quarantine flag. See Yellow flag, under Flag.
 Blue a. [Compar. Bluer superl. Bluest.]
 1. Having the color of the clear sky, or a hue resembling it, whether lighter or darker; as, the deep, blue sea; as blue as a sapphire; blue violets. “The blue firmament.”
 2. Pale, without redness or glare, -- said of a flame; hence, of the color of burning brimstone, betokening the presence of ghosts or devils; as, the candle burns blue; the air was blue with oaths.
 3. Low in spirits; melancholy; as, to feel blue.
 4. Suited to produce low spirits; gloomy in prospect; as, thongs looked blue. [Colloq.]
 5. Severe or over strict in morals; gloom; as, blue and sour religionists; suiting one who is over strict in morals; inculcating an impracticable, severe, or gloomy mortality; as, blue laws.
 6. Literary; -- applied to women; -- an abbreviation of bluestocking. [Colloq.]
    The ladies were very blue and well informed.   --Thackeray.
 Blue asbestus. See Crocidolite.
 Blue black, of, or having, a very dark blue color, almost black.
 Blue blood. See under Blood.
 Blue buck Zool., a small South African antelope (Cephalophus pygmæus); also applied to a larger species (Ægoceras leucophæus); the blaubok.
 Blue cod Zool., the buffalo cod.
 Blue crab Zool., the common edible crab of the Atlantic coast of the United States (Callinectes hastatus).
 Blue curls Bot., a common plant (Trichostema dichotomum), resembling pennyroyal, and hence called also bastard pennyroyal.
 Blue devils, apparitions supposed to be seen by persons suffering with delirium tremens; hence, very low spirits.  “Can Gumbo shut the hall door upon blue devils, or lay them all in a red sea of claret?” --Thackeray.
 Blue gage. See under Gage, a plum.
 Blue gum, an Australian myrtaceous tree (Eucalyptus globulus), of the loftiest proportions, now cultivated in tropical and warm temperate regions for its timber, and as a protection against malaria. The essential oil is beginning to be used in medicine. The timber is very useful. See Eucalyptus.
 Blue jack, Blue stone, blue vitriol; sulphate of copper.
 Blue jacket, a man-of war's man; a sailor wearing a naval uniform.
 Blue jaundice. See under Jaundice.
 Blue laws, a name first used in the eighteenth century to describe certain supposititious laws of extreme rigor reported to have been enacted in New Haven; hence, any puritanical laws. [U. S.]
 Blue light, a composition which burns with a brilliant blue flame; -- used in pyrotechnics and as a night signal at sea, and in military operations.
 Blue mantle Her., one of the four pursuivants of the English college of arms; -- so called from the color of his official robes.
 Blue mass, a preparation of mercury from which is formed the blue pill. --McElrath.
 Blue mold or Blue mould, the blue fungus (Aspergillus glaucus) which grows on cheese. --Brande & C.
 Blue Monday, (a) a Monday following a Sunday of dissipation, or itself given to dissipation (as the Monday before Lent). (b) a Monday considered as depressing because it is a workday in contrast to the relaxation of the weekend.
 Blue ointment Med., mercurial ointment.
 Blue Peter British Marine, a blue flag with a white square in the center, used as a signal for sailing, to recall boats, etc. It is a corruption of blue repeater, one of the British signal flags.
 Blue pill. Med. (a) A pill of prepared mercury, used as an aperient, etc. (b) Blue mass.
 Blue ribbon. (a) The ribbon worn by members of the order of the Garter; -- hence, a member of that order. (b) Anything the attainment of which is an object of great ambition; a distinction; a prize. “These [scholarships] were the --=\blue ribbon of the college.”\= --Farrar. (c) The distinctive badge of certain temperance or total abstinence organizations, as of the --Blue ribbon Army.
 Blue ruin, utter ruin; also, gin. [Eng. Slang] --Carlyle.
 Blue spar Min., azure spar; lazulite. See Lazulite.
 Blue thrush Zool., a European and Asiatic thrush (Petrocossyphus cyaneas).
 Blue verditer. See Verditer.
 Blue vitriol Chem., sulphate of copper, a violet blue crystallized salt, used in electric batteries, calico printing, etc.
 Blue water, the open ocean.
 Big Blue, the International Business Machines corporation. [Wall Street slang.]
 To look blue, to look disheartened or dejected.
 True blue, genuine and thorough; not modified, nor mixed; not spurious; specifically, of uncompromising Presbyterianism, blue being the color adopted by the Covenanters.
 For his religion . . .
 'T was Presbyterian, true blue.   --Hudibras.
 blue jack
      n : small salmon of northern Pacific coasts and the Great Lakes
          [syn: coho, cohoe, coho salmon, silver salmon, Onchorynchus
          kisutch]