The Collaborative International Dictionary of English v.0.48:

Helix \He"lix\, n.; pl. L. Helices, E. Helixes. [L. helix,
   Gr. ?, ?, fr. ? to turn round; cf. L. volvere, and E. volute,
   voluble.]
   1. (Geom.) A nonplane curve whose tangents are all equally
      inclined to a given plane. The common helix is the curve
      formed by the thread of the ordinary screw. It is
      distinguished from the spiral, all the convolutions of
      which are in the plane.
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   2. (Arch.) A caulicule or little volute under the abacus of
      the Corinthian capital.
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   3. (Anat.) The incurved margin or rim of the external ear.
      See Illust. of Ear.
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   4. (Zool.) A genus of land snails, including a large number
      of species.
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   Note: The genus originally included nearly all shells, but is
         now greatly restricted. See Snail, Pulmonifera.
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