The Collaborative International Dictionary of English v.0.48:

Trunkfish \Trunk"fish`\, n. (Zool.)
   Any one of several species of plectognath fishes, belonging
   to the genus Ostracion, or the family Ostraciontidae,
   having an angular body covered with a rigid integument
   consisting of bony scales. Some of the species are called
   also coffer fish, and boxfish.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Cowfish \Cow"fish`\ (kou"f[i^]sh`), n. (Zool.)
   (a) The grampus.
   (b) A California dolphin (Tursiops Gillii).
   (c) A marine plectognath fish (Ostracoin quadricorne, and
       allied species), having two projections, like horns, in
       front; -- called also cuckold, coffer fish,
       trunkfish.
       [1913 Webster]

WordNet (r) 3.0 (2006):

trunkfish
    n 1: any of numerous small tropical fishes having body and head
         encased in bony plates [syn: boxfish, trunkfish]