Octant

Part of speech: noun (n.)

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.