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.
      [1913 Webster]

   2. (Anat.) The kneecap; the kneepan; the cap of the knee.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

patella
    n 1: a small flat triangular bone in front of the knee that
         protects the knee joint [syn: patella, kneecap,
         kneepan]
    2: type genus of the family Patellidae: common European limpets
       [syn: Patella, genus Patella]