The Collaborative International Dictionary of English v.0.48:

Petrel \Pe"trel\, n. [F. p['e]trel; a dim. of the name Peter, L.
   Petrus, Gr. pe`tros a stone (--John i. 42); -- probably so
   called in allusion to St. Peter's walking on the sea. See
   Petrify.] (Zool.)
   Any one of numerous species of longwinged sea birds belonging
   to the family Procellarid[ae]. The small petrels, or Mother
   Carey's chickens, belong to Oceanites, Oceanodroma,
   Procellaria, and several allied genera.
   [1913 Webster]

   Diving petrel, any bird of the genus Pelecanoides. They
      chiefly inhabit the southern hemisphere.

   Fulmar petrel, Giant petrel. See Fulmar.

   Pintado petrel, the Cape pigeon. See under Cape.

   Pintado petrel, any one of several small petrels,
      especially Procellaria pelagica, or Mother Carey's
      chicken, common on both sides of the Atlantic.
      [1913 Webster]

WordNet (r) 3.0 (2006):

diving petrel
    n 1: any of several small diving birds of southern hemisphere
         seas; somewhat resemble auks