WordNet (r) 3.0 (2006):

pitch into
    v 1: hit violently, as in an attack [syn: lam into, tear
         into, lace into, pitch into, lay into]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "pitch into":
   accept, ambush, assail, assault, assume, attack, attempt, blitz,
   buckle to, bushwhack, come at, come down on, crack down on,
   descend on, descend upon, dive into, draw first blood, embark in,
   embark upon, endeavor, engage in, enter on, enter upon, fall into,
   fall on, fall to, fall upon, gang up on, get busy, get cracking,
   get going, get under way, get with it, go about, go at, go for,
   go in for, go into, go to it, go upon, harry, have at, hit,
   hit like lightning, hop to it, jump, jump to it, land on,
   launch forth, launch into, lay about, lay about one, lay at,
   lay hands on, lay into, lay on, light into, make war on, move into,
   mug, pitch in, plunge into, pounce upon, pound, proceed to,
   sail into, set about, set at, set forward, set going, set on,
   set to, set to work, set upon, square up, start in, strike,
   surprise, swoop down on, tackle, take on, take the offensive,
   take up, turn to, undertake, venture upon, wade into