WordNet (r) 3.0 (2006):

pitch in
    v 1: eat heartily; "The food was placed on the table and the
         children pitched in" [syn: pitch in, dig in]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "pitch in":
   attack, begin, blast away, blast off, break bread, buckle down,
   commence, count calories, diet, dive in, dive into, eat, enter on,
   enter upon, fall to, fare, feed, get busy, get cracking, get going,
   get to, get with it, go ahead, go to it, head into, hop to it,
   hunger, jump in, jump off, jump to it, kick off, launch,
   launch into, light into, partake, partake of, pitch into,
   plunge into, relish, sail into, savor, send off, set about, set at,
   set in, set out, set sail, set to, set to work, start, start in,
   start off, start out, subscribe, tackle, take, take off, take on,
   taste, turn to, undertake, wade into