The Collaborative International Dictionary of English v.0.48:

Stickleback \Stic"kle*back`\, n. [OE. & Prov E. stickle a
   prickle, spine, sting (AS. sticel) + back. See Stick, v.
   t., and cf. Banstickle.] (Zool.)
   Any one of numerous species of small fishes of the genus
   Gasterosteus and allied genera. The back is armed with two
   or more sharp spines. They inhabit both salt and brackish
   water, and construct curious nests. Called also sticklebag,
   sharpling, and prickleback.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stickleback
    n 1: small (2-4 inches) pugnacious mostly scaleless spiny-backed
         fishes of northern fresh and littoral waters having
         elaborate courtship; subjects of much research [syn:
         stickleback, prickleback]