- the eighth part of a circle.
- Mathematics. any of the eight parts into which three mutually perpendicular planes divide space.
- an instrument having an arc of 24°, used by navigators for measuring angles up to 90°.
- the position of one heavenly body when 45° distant from another.
- (initial capital letter) Astronomy. the constellation Octans.
Origin of octant
1680–90; < Latin octant- (stem of octāns); see Octans
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for octant
Excluded, of course, are those instruments normally made of wood, such as the octant and the mariners quadrant.
Octant made of dark wood and with lignum vitae; brass fittings.
It was in its octant, and showed a crescent finely traced on the dark background of the sky.
The flat bar which carries the nonius scale and index-glass of a quadrant, octant, quintant, or sextant.The Sailor's Word-Book
William Henry Smyth
Thus fig. 59 conveniently represents an octant of the wave surface, which cuts each coordinate plane in a circle and an ellipse.
- any of the eight parts into which the three planes containing the Cartesian coordinate axes divide space
- an eighth part of a circle
- astronomy the position of a celestial body when it is at an angular distance of 45° from another body
- an instrument used for measuring angles, similar to a sextant but having a graduated arc of 45°
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
Word Origin and History for octant
Online Etymology Dictionary, © 2010 Douglas Harper