The Collaborative International Dictionary of English v.0.48:

Patella \Pa*tel"la\, n.; pl. Patell[ae]. [L., a small pan, the
   kneepan, dim. of patina, patena, a pan, dish.]
   1. A small dish, pan, or vase.
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   2. (Anat.) The kneecap; the kneepan; the cap of the knee.
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   3. (Zool.) A genus of marine gastropods, including many
      species of limpets. The shell has the form of a flattened
      cone. The common European limpet (Patella vulgata) is
      largely used for food.
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   4. (Bot.) A kind of apothecium in lichens, which is
      orbicular, flat, and sessile, and has a special rim not a
      part of the thallus.
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