octant Meaning, Definition & Usage

  1. noun a measuring instrument for measuring angles to a celestial body; similar to a sextant but with 45 degree calibration

WordNet

Oc"tant noun
Etymology
L. octans, -antis. fr. octo eight. See Octave.
Definitions
  1. (Geom.) The eighth part of a circle; an arc of 45 degrees.
  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.
  3. An instrument for measuring angles (generally called a quadrant), having an arc which measures up to 9O°, but being itself the eighth part of a circle. Cf. Sextant.
  4. (Math. & Crystallog.) One of the eight parts into which a space is divided by three coördinate planes.

Webster 1913