Source : Webster's Revised Unabridged Dictionary (1913)

Threadfish \Thread"fish`\, n. (Zo["o]l.)
   (a) The cutlass fish.
   (b) A carangoid fish ({Caranx gallus}, or {C. crinitus})
       having the anterior rays of the soft dorsal and anal fins
       prolonged in the form of long threads.

Source : WordNet®

threadfish
     n : fish having greatly elongated front rays on dorsal and anal
         fins [syn: {thread-fish}, {Alectis ciliaris}]