Annulus

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

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.