The Collaborative International Dictionary of English v.0.48:

Pun \Pun\, v. i. [imp. & p. p. Punned; p. pr. & vb. n.
   Punning.]
   To make puns, or a pun; to use a word in a double sense,
   especially when the contrast of ideas is ludicrous; to play
   upon words; to quibble. --Dryden.
   [1913 Webster]

WordNet (r) 3.0 (2006):

punning
    n 1: a humorous play on words; "I do it for the pun of it"; "his
         constant punning irritated her" [syn: pun, punning,
         wordplay, paronomasia]