The Collaborative International Dictionary of English v.0.48:

housebreak \house"break`\ v. t.
   to train a pet to live cleanly in a house, especially by
   training it to defecate and urinate in designated boxes.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

housebreak
    v 1: train (a pet) to live cleanly in a house [syn:
         housebreak, house-train]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "housebreak":
   acclimate, acclimatize, accommodate, accustom, adapt, adjust,
   apprentice, break, break in, break to harness, breed, bring up,
   bust, case harden, condition, confirm, cultivate, develop,
   discipline, domesticate, domesticize, drill, establish, exercise,
   familiarize, fetch up, fit, fix, form, foster, gentle, groom,
   habituate, harden, house-train, improve, inure, knock over,
   lick into shape, naturalize, nurse, nurture, orient, orientate,
   practice, prepare, put in tune, put to school, raise, ransack,
   ready, rear, rehearse, rifle, rob, season, send to school,
   take in hand, tame, train, wont