An·nu·lus n.; pl. Annuli
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. Zool. Ring-shaped structures or markings, found in, or upon, various animals.
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annulus
n 1: a toroidal shape; "a ring of ships in the harbor"; "a halo
of smoke" [syn: ring, halo, anulus, doughnut, anchor
ring]
2: (Fungi) remnant of the partial veil that in mature mushrooms
surrounds the lower part of the stem
[also: annuli (pl)]