WordNet (r) 3.0 (2006):

warhorse
    n 1: a work of art (composition or drama) that is part of the
         standard repertory but has become hackneyed from much
         repetition
    2: an experienced person who has been through many battles;
       someone who has given long service [syn: veteran, old-
       timer, oldtimer, old hand, warhorse, old stager,
       stager]
    3: horse used in war