Source : Webster's Revised Unabridged Dictionary (1913)

Cingulum \Cin"gu*lum\, n. [L., a girdle.] (Zo["o]l.)
   (a) A distinct girdle or band of color; a raised spiral line
       as seen on certain univalve shells.
   (b) The clitellus of earthworms.
   (c) The base of the crown of a tooth.

Source : WordNet®

cingulum
     n : (anatomy) an encircling girdle-like structure (as the ridge
         around the base of a tooth)
     [also: {cingula} (pl)]