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]