The Collaborative International Dictionary of English v.0.48:

otterhound \otterhound\, otter hound \otter hound\n.
   1. A small hardy British hound having long pendulous ears and
      a thick coarse shaggy coat with an oily undercoat; bred in
      England for hunting otters. Called also otter dog.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

otterhound
    n 1: hardy British hound having long pendulous ears and a thick
         coarse shaggy coat with an oily undercoat; bred for hunting
         otters [syn: otterhound, otter hound]