O·pen a.
 1. Free of access; not shut up; not closed; affording unobstructed ingress or egress; not impeding or preventing passage; not locked up or covered over; -- applied to passageways; as, an open door, window, road, etc.; also, to inclosed structures or objects; as, open houses, boxes, baskets, bottles, etc.; also, to means of communication or approach by water or land; as, an open harbor or roadstead.
 Through the gate,
 Wide open and unguarded, Satan passed.   --Milton
 Note: Also, figuratively, used of the ways of communication of the mind, as by the senses; ready to hear, see, etc.; as, to keep one's eyes and ears open.
    His ears are open unto their cry.   --Ps. xxxiv. 15.
 2. Free to be used, enjoyed, visited, or the like; not private; public; unrestricted in use; as, an open library, museum, court, or other assembly; liable to the approach, trespass, or attack of any one; unprotected; exposed.
    If Demetrius . . . have a matter against any man, the law is open and there are deputies.   --Acts xix. 33.
 The service that I truly did his life,
 Hath left me open to all injuries.   --Shak.
 3. Free or cleared of obstruction to progress or to view; accessible; as, an open tract; the open sea.
 4. Not drawn together, closed, or contracted; extended; expanded; as, an open hand; open arms; an open flower; an open prospect.
    Each, with open arms, embraced her chosen knight.   --Dryden.
 5. Hence: (a) Without reserve or false pretense; sincere; characterized by sincerity; unfeigned; frank; also, generous; liberal; bounteous; -- applied to personal appearance, or character, and to the expression of thought and feeling, etc.
    With aspect open, shall erect his head.   --Pope.
    The Moor is of a free and open nature.   --Shak.
    The French are always open, familiar, and talkative.   --Addison.
 (b) Not concealed or secret; not hidden or disguised; exposed to view or to knowledge; revealed; apparent; as, open schemes or plans; open shame or guilt; open source code.
    His thefts are too open.   --Shak.
 That I may find him, and with secret gaze
 Or open admiration him behold.   --Milton.
 6. Not of a quality to prevent communication, as by closing water ways, blocking roads, etc.; hence, not frosty or inclement; mild; -- used of the weather or the climate; as, an open season; an open winter.
 7. Not settled or adjusted; not decided or determined; not closed or withdrawn from consideration; as, an open account; an open question; to keep an offer or opportunity open.
 8. Free; disengaged; unappropriated; as, to keep a day open for any purpose; to be open for an engagement.
 9. Phon. (a) Uttered with a relatively wide opening of the articulating organs; -- said of vowels; as, the än fär is open as compared with the ā in sāy. (b) Uttered, as a consonant, with the oral passage simply narrowed without closure, as in uttering s.
 10. Mus. (a) Not closed or stopped with the finger; -- said of the string of an instrument, as of a violin, when it is allowed to vibrate throughout its whole length. (b) Produced by an open string; as, an open tone.
 The open air, the air out of doors.
 Open chain. Chem. See Closed chain, under Chain.
 Open circuit Elec., a conducting circuit which is incomplete, or interrupted at some point; -- opposed to an uninterrupted, or closed circuit.
 Open communion, communion in the Lord's supper not restricted to persons who have been baptized by immersion.  Cf. Close communion, under Close, a.
 Open diapason Mus., a certain stop in an organ, in which the pipes or tubes are formed like the mouthpiece of a flageolet at the end where the wind enters, and are open at the other end.
 Open flank Fort., the part of the flank covered by the orillon.
 Open-front furnace Metal., a blast furnace having a forehearth.
 Open harmony Mus., harmony the tones of which are widely dispersed, or separated by wide intervals.
 Open hawse Naut., a hawse in which the cables are parallel or slightly divergent.  Cf. Foul hawse, under Hawse.
 Open hearth Metal., the shallow hearth of a reverberatory furnace.
 Open-hearth furnace, a reverberatory furnace; esp., a kind of reverberatory furnace in which the fuel is gas, used in manufacturing steel.
 Open-hearth process Steel Manuf., a process by which melted cast iron is converted into steel by the addition of wrought iron, or iron ore and manganese, and by exposure to heat in an open-hearth furnace; -- also called the Siemens-Martin process, from the inventors.
 Open-hearth steel, steel made by an open-hearth process; -- also called Siemens-Martin steel.
 Open newel. Arch. See Hollow newel, under Hollow.
 Open pipe Mus., a pipe open at the top. It has a pitch about an octave higher than a closed pipe of the same length.
 Open-timber roof Arch., a roof of which the constructional parts, together with the under side of the covering, or its lining, are treated ornamentally, and left to form the ceiling of an apartment below, as in a church, a public hall, and the like.
 Open vowel or Open consonant. See Open, a., 9.
 Note: ☞ Open is used in many compounds, most of which are self-explaining; as, open-breasted, open-minded.
 Syn: -- Unclosed; uncovered; unprotected; exposed; plain; apparent; obvious; evident; public; unreserved; frank; sincere; undissembling; artless. See Candid, and Ingenuous.
 Chain n.
 1. A series of links or rings, usually of metal, connected, or fitted into one another, used for various purposes, as of support, of restraint, of ornament, of the exertion and transmission of mechanical power, etc.
    [They] put a chain of gold about his neck.   --Dan. v. 29.
 2. That which confines, fetters, or secures, as a chain; a bond; as, the chains of habit.
 Driven down
 To chains of darkness and the undying worm.   --Milton.
 3. A series of things linked together; or a series of things connected and following each other in succession; as, a chain of mountains; a chain of events or ideas.
 4. Surv. An instrument which consists of links and is used in measuring land.
 Note: ☞ One commonly in use is Gunter's chain, which consists of one hundred links, each link being seven inches and ninety-two one hundredths in length; making up the total length of rods, or sixty-six, feet; hence, a measure of that length; hence, also, a unit for land measure equal to four rods square, or one tenth of an acre.
 5. pl. Naut. Iron links bolted to the side of a vessel to bold the dead-eyes connected with the shrouds; also, the channels.
 6. Weaving The warp threads of a web.
 Chain belt Mach., a belt made of a chain; -- used for transmitting power.
 Chain boat, a boat fitted up for recovering lost cables, anchors, etc.
 Chain bolt (a) Naut. The bolt at the lower end of the chain plate, which fastens it to the vessel's side. (b) A bolt with a chain attached for drawing it out of position.
 Chain bond. See Chain timber.
 Chain bridge, a bridge supported by chain cables; a suspension bridge.
 Chain cable, a cable made of iron links.
 Chain coral Zool., a fossil coral of the genus Halysites, common in the middle and upper Silurian rocks. The tubular corallites are united side by side in groups, looking in an end view like links of a chain. When perfect, the calicles show twelve septa.
 Chain coupling. (a) A shackle for uniting lengths of chain, or connecting a chain with an object. (b) Railroad Supplementary coupling together of cars with a chain.
 Chain gang, a gang of convicts chained together.
 Chain hook Naut., a hook, used for dragging cables about the deck.
 Chain mail, flexible, defensive armor of hammered metal links wrought into the form of a garment.
 Chain molding Arch., a form of molding in imitation of a chain, used in the Normal style.
 Chain pier, a pier suspended by chain.
 Chain pipe Naut., an opening in the deck, lined with iron, through which the cable is passed into the lockers or tiers.
 Chain plate Shipbuilding, one of the iron plates or bands, on a vessel's side, to which the standing rigging is fastened.
 Chain pulley, a pulley with depressions in the periphery of its wheel, or projections from it, made to fit the links of a chain.
 Chain pumps. See in the Vocabulary.
 Chain rule Arith., a theorem for solving numerical problems by composition of ratios, or compound proportion, by which, when several ratios of equality are given, the consequent of each being the same as the antecedent of the next, the relation between the first antecedent and the last consequent is discovered.
 Chain shot Mil., two cannon balls united by a shot chain, formerly used in naval warfare on account of their destructive effect on a ship's rigging.
 Chain stitch. See in the Vocabulary.
 Chain timber. Arch. See Bond timber, under Bond.
 Chain wales. Naut. Same as Channels.
 Chain wheel. See in the Vocabulary.
 Closed chain, Open chain Chem., terms applied to the chemical structure of compounds whose rational formulæ are written respectively in the form of a closed ring (see Benzene nucleus, under Benzene), or in an open extended form.
 Endless chain, a chain whose ends have been united by a link.
 closed chain
      n : (chemistry) a chain of atoms in a molecule that forms a
          closed loop [syn: ring] [ant: open chain]