The Collaborative International Dictionary of English v.0.48:

Avocado \Av`o*ca"do\, n. [Corrupted from the Mexican ahuacatl:
   cf. Sp. aguacate, F. aguacat['e], avocat, G. avogadobaum.]
   The pulpy fruit of Persea gratissima, a tree of tropical
   America. It is about the size and shape of a large pear; --
   called also avocado pear, alligator pear, midshipman's
   butter.
   [1913 Webster]

WordNet (r) 3.0 (2006):

avocado pear
    n 1: a pear-shaped tropical fruit with green or blackish skin
         and rich yellowish pulp enclosing a single large seed [syn:
         avocado, alligator pear, avocado pear, aguacate]