octant

• POS: Noun
• HYPHEN: oc=tant

CIDE DICTIONARY

octant, n. [L. octans, -antis. fr. octo eight. See Octave.].

•  The eighth part of a circle; an arc of 45 degrees.  [1913 Webster]
•  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]
•  An instrument for measuring angles (generally called a quadrant), having an arc which measures up to 9OSextant.  [1913 Webster]
•  One of the eight parts into which a space is divided by three coördinate planes.  [1913 Webster]

OXFORD DICTIONARY

octant, n.
1 an arc of a circle equal to one eighth of the circumference.
2 such an arc with two radii, forming an area equal to one eighth of the circle.
3 each of eight parts into which three planes intersecting (esp. at right angles) at a point divide the space or the solid body round it.
4 Astron. a point in a body's apparent course 45° distant from a given point, esp. a point at which the moon is 45° from conjunction or opposition with the sun.
5 an instrument in the form of a graduated eighth of a circle, used in astronomy and navigation.

Etymology

L octans octant- half-quadrant f. octo eight