[ 'ɒkt(ə)nt ]
■ noun
1》 an arc of a circle equal to one eighth of its circumference, or the area enclosed by such an arc with two radii of the circle.
2》 each of eight parts into which a space or solid body is divided by three planes which intersect (especially at right angles) at a single point.
3》 an obsolete instrument in the form of a graduated eighth of a circle, used in astronomy and navigation.
Origin
C17: from L. octans , ~- 'half-quadrant', from octo 'eight'.