Octant

1. n. One of the eight parts into which a space is divided by three coordinate planes.
2. n. The eighth part of a circle; an arc of 45 degrees.
3. n. 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.
4. n. 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.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.