The Collaborative International Dictionary of English v.0.48:

frankfurter \frank"fur*ter\
   A small cooked sausage of beef or beef and pork, usually 5 to
   6 inches, sometimes as long as 12 inches in length; called
   also frankforter, frankfort, frankfurt. It is commonly
   eaten on a roll, called a hot dog bun.

   Syn: wiener, hot dog[1].
        [PJC]

WordNet (r) 3.0 (2006):

frankfurter
    n 1: a smooth-textured sausage of minced beef or pork usually
         smoked; often served on a bread roll [syn: frank,
         frankfurter, hotdog, hot dog, dog, wiener,
         wienerwurst, weenie]