annulus

1. A ring; a ringlike part or space. 2. (Geom.) (a) A space contained between the circumferences of two circles, one within the other. (b) The solid formed by a circle revolving around a line which is the plane of the circle but does not cut it. 3. (Zoöl.) Ring-shaped structures or markings, found in, or upon, various animals.

Source: Webster's Revised Unabridged Dictionary (1913), United States public domain. See methodology for full licensing detail. Word validity for game play may differ from any official game dictionary.