The Collaborative International Dictionary of English v.0.48:

leatherjack \leatherjack\ n.
   any of several New World tropical fishes having tiny embedded
   scales; the leatherjacket[2].

   Syn: leatherjacket.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

leatherjack
    n 1: any of several New World tropical fishes having tiny
         embedded scales [syn: leatherjacket, leatherjack]