Octant
Octant , noun
[Latin octans, -antis. from octo eight. See Octave.]
1.
(Geometry) The eighth part of a circle; an arc of 45 degrees.
2.
(Astronomy & Astrology) 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. Compare Sextant.
4.
(Mathematics & Crystallography) One of the eight parts into which a space is divided by three coordinate planes.