1. a quarter of the circumference of a circle;

[syn:

2. any of the four areas into which a plane is divided by two orthogonal coordinate axes;

3. the area enclosed by two perpendicular radii of a circle;

4. a measuring instrument for measuring altitude of heavenly bodies;

The Collaborative International Dictionary of English v.0.48:

Octant \Oc"tant\, n. [L. octans, -antis. fr. octo eight. See Octave.] 1. (Geom.) The eighth part of a circle; an arc of 45 degrees. [1913 Webster] 2. (Astron. & Astrol.) The position or aspect of a heavenly body, as the moon or a planet, when half way between conjunction, or opposition, and quadrature, or distant from another body 45 degrees. [1913 Webster] 3. An instrument for measuring angles (generally called a quadrant), having an arc which measures up to 9O[deg], but being itself the eighth part of a circle. Cf. Sextant. [1913 Webster] 4. (Math. & Crystallog.) One of the eight parts into which a space is divided by three coordinate planes. [1913 Webster]The Collaborative International Dictionary of English v.0.48:

Quadrant \Quad"rant\, n. [L. quadrans, -antis, a fourth part, a fourth of a whole, fr. quattuor four: cf. F. quadrant, cadran. See Four, and cf. Cadrans.] 1. The fourth part; the quarter. [Obs.] --Sir T. Browne. [1913 Webster] 2. (Geom.) The quarter of a circle, or of the circumference of a circle, an arc of 90[deg], or one subtending a right angle at the center. [1913 Webster] 3. (Anal. (Geom.) One of the four parts into which a plane is divided by the coordinate axes. The upper right-hand part is the first quadrant; the upper left-hand part the second; the lower left-hand part the third; and the lower right-hand part the fourth quadrant. [1913 Webster] 4. An instrument for measuring altitudes, variously constructed and mounted for different specific uses in astronomy, surveying, gunnery, etc., consisting commonly of a graduated arc of 90[deg], with an index or vernier, and either plain or telescopic sights, and usually having a plumb line or spirit level for fixing the vertical or horizontal direction. [1913 Webster] Gunner's quadrant, an instrument consisting of a graduated limb, with a plumb line or spirit level, and an arm by which it is applied to a cannon or mortar in adjusting it to the elevation required for attaining the desired range. Gunter's quadrant. See Gunter's quadrant, in the Vocabulary. Hadley's quadrant, a hand instrument used chiefly at sea to measure the altitude of the sun or other celestial body in ascertaining the vessel's position. It consists of a frame in the form of an octant having a graduated scale upon its arc, and an index arm, or alidade pivoted at its apex. Mirrors, called the index glass and the horizon glass, are fixed one upon the index arm and the other upon one side of the frame, respectively. When the instrument is held upright, the index arm may be swung so that the index glass will reflect an image of the sun upon the horizon glass, and when the reflected image of the sun coincides, to the observer's eye, with the horizon as seen directly through an opening at the side of the horizon glass, the index shows the sun's altitude upon the scale; -- more properly, but less commonly, called an octant. Quadrant of altitude, an appendage of the artificial globe, consisting of a slip of brass of the length of a quadrant of one of the great circles of the globe, and graduated. It may be fitted to the meridian, and being movable round to all points of the horizon, serves as a scale in measuring altitudes, azimuths, etc. [1913 Webster]WordNet (r) 3.0 (2006):

quadrant n 1: a quarter of the circumference of a circle [syn: quadrant, quarter-circle] 2: any of the four areas into which a plane is divided by two orthogonal coordinate axes 3: the area enclosed by two perpendicular radii of a circle 4: a measuring instrument for measuring altitude of heavenly bodiesMoby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "quadrant": adjunct, astrolabe, azimuth circle, azimuth compass, bevel, bevel protractor, bevel square, clinometer, component, contingent, crescent, cross section, detachment, detail, division, dole, fraction, goniometer, graphometer, half circle, hemicycle, installment, item, pantometer, parcel, part, particular, percentage, portion, protractor, quarter, quota, radiogoniometer, random sample, remainder, sample, sampling, section, sector, segment, semicircle, sextant, share, subdivision, subgroup, subspecies, theodolite, transit, transit circle, transit instrument, transit theodoliteBouvier's Law Dictionary, Revised 6th Ed (1856):

QUADRANT. In angular measures, a quadrant is equal to ninety degrees. Vide Measure.