The Collaborative International Dictionary of English v.0.48:

Cockle \Coc"kle\ (k[o^]k"k'l), n. [OE. cockes cockles, AS.
   s[=ae]coccas sea cockles, prob, from Celtic; cf. W. cocs
   cockles, Gael. cochull husk. Perh. influenced by F. coquille
   shell, a dim. from the root of E. conch. Cf. Coach.]
   1. (Zool.) A bivalve mollusk, with radiating ribs, of the
      genus Cardium, especially Cardium edule, used in
      Europe for food; -- sometimes applied to similar shells of
      other genera.
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   2. A cockleshell.
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   3. The mineral black tourmaline or schorl; -- so called by
      the Cornish miners. --Raymond.
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   4. The fire chamber of a furnace. [Eng.] --Knight.
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   5. A hop-drying kiln; an oast. --Knight.
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   6. The dome of a heating furnace. --Knight.
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   Cockle hat, a hat ornamented with a cockleshell, the badge
      of a pilgrim. --Shak.

   Cockle stairs, winding or spiral stairs.
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WordNet (r) 3.0 (2006):

Cardium edule
    n 1: common edible European cockle [syn: edible cockle,
         Cardium edule]