[1] : The Collaborative International Dictionary of English v.0.48

annulus \an"nulus\, n.; pl. annuli. l.
   1. a ring; a ringlike part or space.
      1913 webster

   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.
          1913 webster

   3. zool. ring-shaped structures or markings, found in, or
      upon, various animals.
      1913 webster
see also:
annuli 

[2] : WordNet (r) 2.0

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
see also:
ring halo anulus doughnut anchor ring annuli 

Annulus >> A Words
Annulus, definition of term: Annulus
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