octant

octant is a Noun

Definition:

[1] The eighth part of a circle; an arc of 45 degrees.

[2] 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 9Oº, but being itself the eighth part of a circle. Cf. Sextant.

[4] One of the eight parts into which a space is divided by three coördinate planes.