[ ok-tuhnt ]

  1. the eighth part of a circle.

  2. Mathematics. any of the eight parts into which three mutually perpendicular planes divide space.

  1. an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.

  2. the position of one heavenly body when 45° distant from another.

  3. Octant, Astronomy. the constellation Octans.

Origin of octant

First recorded in 1680–90; from Latin octant- (stem of octāns ); see Octans

Other words from octant

  • oc·tan·tal [ok-tan-tl], /ɒkˈtæn tl/, adjective

Words Nearby octant

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use octant in a sentence

British Dictionary definitions for octant


/ (ˈɒktənt) /

  1. maths

    • any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space

    • an eighth part of a circle

  2. astronomy the position of a celestial body when it is at an angular distance of 45° from another body

  1. an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°

Origin of octant

C17: from Latin octans half quadrant, from octo eight

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012