Pitch, n.
 1. A throw; a toss; a cast, as of something from the hand; as, a good pitch in quoits.
 Pitch and toss, a game played by tossing up a coin, and calling “Heads or tails;” hence: To play pitch and toss with (anything), to be careless or trust to luck about it. “To play pitch and toss with the property of the country.” --G. Eliot.
 Pitch farthing. See Chuck farthing, under 5th Chuck.
 2. Cricket That point of the ground on which the ball pitches or lights when bowled.
 3. A point or peak; the extreme point or degree of elevation or depression; hence, a limit or bound.
 Driven headlong from the pitch of heaven, down
 Into this deep.   --Milton.
    Enterprises of great pitch and moment.   --Shak.
    To lowest pitch of abject fortune.   --Milton.
    He lived when learning was at its highest pitch.   --Addison.
    The exact pitch, or limits, where temperance ends.   --Sharp.
 4. Height; stature. [Obs.]
 5. A descent; a fall; a thrusting down.
 6. The point where a declivity begins; hence, the declivity itself; a descending slope; the degree or rate of descent or slope; slant; as, a steep pitch in the road; the pitch of a roof.
 7. Mus. The relative acuteness or gravity of a tone, determined by the number of vibrations which produce it; the place of any tone upon a scale of high and low.
 Note: ☞ Musical tones with reference to absolute pitch, are named after the first seven letters of the alphabet; with reference to relative pitch, in a series of tones called the scale, they are called one, two, three, four, five, six, seven, eight. Eight is also one of a new scale an octave higher, as one is eight of a scale an octave lower.
 8. Mining The limit of ground set to a miner who receives a share of the ore taken out.
 9. Mech. (a) The distance from center to center of any two adjacent teeth of gearing, measured on the pitch line; -- called also circular pitch. (b) The length, measured along the axis, of a complete turn of the thread of a screw, or of the helical lines of the blades of a screw propeller. (c) The distance between the centers of holes, as of rivet holes in boiler plates.
 10. Elec. The distance between symmetrically arranged or corresponding parts of an armature, measured along a line, called the pitch line, drawn around its length. Sometimes half of this distance is called the pitch.
 Concert pitch Mus., the standard of pitch used by orchestras, as in concerts, etc.
 Diametral pitch Gearing, the distance which bears the same relation to the pitch proper, or circular pitch, that the diameter of a circle bears to its circumference; it is sometimes described by the number expressing the quotient obtained by dividing the number of teeth in a wheel by the diameter of its pitch circle in inches; as, 4 pitch, 8 pitch, etc.
 Pitch chain, a chain, as one made of metallic plates, adapted for working with a sprocket wheel.
 Pitch line, or Pitch circle Gearing, an ideal line, in a toothed gear or rack, bearing such a relation to a corresponding line in another gear, with which the former works, that the two lines will have a common velocity as in rolling contact; it usually cuts the teeth at about the middle of their height, and, in a circular gear, is a circle concentric with the axis of the gear; the line, or circle, on which the pitch of teeth is measured.
 Pitch of a roof Arch., the inclination or slope of the sides expressed by the height in parts of the span; as, one half pitch; whole pitch; or by the height in parts of the half span, especially among engineers; or by degrees, as a pitch of 30°, of 45°, etc.; or by the rise and run, that is, the ratio of the height to the half span; as, a pitch of six rise to ten run. Equilateral pitch is where the two sloping sides with the span form an equilateral triangle.
 Pitch of a plane Carp., the slant of the cutting iron.
 Pitch of poles Elec., the distance between a pair of poles of opposite sign.
 Pitch pipe, a wind instrument used by choristers in regulating the pitch of a tune.
 Pitch point Gearing, the point of contact of the pitch lines of two gears, or of a rack and pinion, which work together.

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 Cir·cle n.
 1. A plane figure, bounded by a single curve line called its circumference, every part of which is equally distant from a point within it, called the center.
 2. The line that bounds such a figure; a circumference; a ring.
 3. Astron. An instrument of observation, the graduated limb of which consists of an entire circle.
 Note: ☞ When it is fixed to a wall in an observatory, it is called a mural circle; when mounted with a telescope on an axis and in Y's, in the plane of the meridian, a meridian  circle or transit circle; when involving the principle of reflection, like the sextant, a reflecting circle; and when that of repeating an angle several times continuously along the graduated limb, a repeating circle.
 4. A round body; a sphere; an orb.
    It is he that sitteth upon the circle of the earth.   --Is. xi. 22.
 5. Compass; circuit; inclosure.
    In the circle of this forest.   --Shak.
 6. A company assembled, or conceived to assemble, about a central point of interest, or bound by a common tie; a class or division of society; a coterie; a set.
    As his name gradually became known, the circle of his acquaintance widened.   --Macaulay.
 7. A circular group of persons; a ring.
 8. A series ending where it begins, and repeating itself.
    Thus in a circle runs the peasant's pain.   --Dryden.
 9. Logic A form of argument in which two or more unproved statements are used to prove each other; inconclusive reasoning.
    That heavy bodies descend by gravity; and, again, that gravity is a quality whereby a heavy body descends, is an impertinent circle and teaches nothing.   --Glanvill.
 10. Indirect form of words; circumlocution. [R.]
 Has he given the lie,
 In circle, or oblique, or semicircle.   --J. Fletcher.
 11. A territorial division or district.
 Note: ☞ The Circles of the Holy Roman Empire, ten in number, were those principalities or provinces which had seats in the German Diet.
 Azimuth circle. See under Azimuth.
 Circle of altitude Astron., a circle parallel to the horizon, having its pole in the zenith; an almucantar.
 Circle of curvature. See Osculating circle of a curve (Below).
 Circle of declination. See under Declination.
 Circle of latitude. (a) Astron. A great circle perpendicular to the plane of the ecliptic, passing through its poles. (b) Spherical Projection A small circle of the sphere whose plane is perpendicular to the axis.
 Circles of longitude, lesser circles parallel to the ecliptic, diminishing as they recede from it.
 Circle of perpetual apparition, at any given place, the boundary of that space around the elevated pole, within which the stars never set. Its distance from the pole is equal to the latitude of the place.
 Circle of perpetual occultation, at any given place, the boundary of the space around the depressed pole, within which the stars never rise.
 Circle of the sphere, a circle upon the surface of the sphere, called a great circle when its plane passes through the center of the sphere; in all other cases, a small circle.
 Diurnal circle. See under Diurnal.
 Dress circle, a gallery in a theater, generally the one containing the prominent and more expensive seats.
 Druidical circles Eng. Antiq., a popular name for certain ancient inclosures formed by rude stones circularly arranged, as at Stonehenge, near Salisbury.
 Family circle, a gallery in a theater, usually one containing inexpensive seats.
 Horary circles Dialing, the lines on dials which show the hours.
 Osculating circle of a curve Geom., the circle which touches the curve at some point in the curve, and close to the point more nearly coincides with the curve than any other circle. This circle is used as a measure of the curvature of the curve at the point, and hence is called circle of curvature.
 Pitch circle. See under Pitch.
 Vertical circle, an azimuth circle.
 Voltaic circuit or Voltaic circle. See under Circuit.
 To square the circle. See under Square.
 Syn: -- Ring; circlet; compass; circuit; inclosure.