From HomoExcelsior

1. One eighth of a circle. 2. A 45 arc. 3. The area enclosed by two radii at a 45 angle and the intersected arc. 4. An instrument based on the principle of the sextant but employing only a 45 angle, used as an aid in navigation. 5. The position of a celestial body when it is separated from another by a 45 angle. 6. One of eight parts into which three-dimensional space is divided by three usually perpendicular coordinate planes.

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