The Collaborative International Dictionary of English v.0.48:

Cheek \Cheek\ (ch[=e]k), n. [OE. cheke, cheoke, AS. ce[`a]ce,
   ce[`o]ce; cf. Goth. kukjan to kiss, D. kaak cheek; perh. akin
   to E. chew, jaw.]
   1. The side of the face below the eye.
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   2. The cheek bone. [Obs.] --Caucer.
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   3. pl. (Mech.) Those pieces of a machine, or of any timber,
      or stone work, which form corresponding sides, or which
      are similar and in pair; as, the cheeks (jaws) of a vise;
      the cheeks of a gun carriage, etc.
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   4. pl. The branches of a bridle bit. --Knight.
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   5. (Founding) A section of a flask, so made that it can be
      moved laterally, to permit the removal of the pattern from
      the mold; the middle part of a flask.
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   6. Cool confidence; assurance; impudence. [Slang]
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   Cheek of beef. See Illust. of Beef.

   Cheek bone (Anat.) the bone of the side of the face; esp.,
      the malar bone.

   Cheek by jowl, side by side; very intimate.

   Cheek pouch (Zool.), a sacklike dilation of the cheeks of
      certain monkeys and rodents, used for holding food.

   Cheeks of a block, the two sides of the shell of a tackle
      block.

   Cheeks of a mast, the projection on each side of a mast,
      upon which the trestletrees rest.

   Cheek tooth (Anat.), a hinder or molar tooth.

   Butment cheek. See under Butment.
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WordNet (r) 3.0 (2006):

cheek pouch
    n 1: a membranous pouch inside the mouth of many rodents (as a
         gopher)