WordNet (r) 3.0 (2006):

asshole
    n 1: insulting terms of address for people who are stupid or
         irritating or ridiculous [syn: asshole, bastard,
         cocksucker, dickhead, shit, mother fucker,
         motherfucker, prick, whoreson, son of a bitch,
         SOB]
    2: vulgar slang for anus [syn: arse, arsehole, asshole,
       bunghole]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "asshole":
   anus, boob, booby, bung, bunghole, chump, ding-a-ling, dingbat,
   dingdong, galoot, goof, jerk, jerk-off, klutz, mutt, prize sap,
   sap, saphead, sawney, schlemiel