Octant

·noun The eighth part of a circle; an arc of 45 degrees.

II. Octant ·noun One of the eight parts into which a space is divided by three coordinate planes.

III. Octant ·noun 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. ·cf. Sextant.

IV. Octant ·noun 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.