The Collaborative International Dictionary of English v.0.48:
Lopeared \Lop"eared`\, Lop-eared \Lop"-eared`\, a. Having ears which droop or hang down; as, a lop-eared hound. [1913 Webster + WordNet 1.5]WordNet (r) 3.0 (2006):
lop-eared adj 1: having bent or drooping ears; "a lop-eared hound"