The Collaborative International Dictionary of English v.0.48:

Pipefish \Pipe"fish`\, n. (Zool.)
   Any lophobranch fish of the genus Siphostoma, or
   Syngnathus, and allied genera, having a long and very
   slender angular body, covered with bony plates. The mouth is
   small, at the end of a long, tubular snout. The male has a
   pouch on his belly, in which the incubation of the eggs takes
   place.
   [1913 Webster] Pipelayer

WordNet (r) 3.0 (2006):

pipefish
    n 1: fish with long tubular snout and slim body covered with
         bony plates [syn: pipefish, needlefish]