The Collaborative International Dictionary of English v.0.48:

Hemibranchi \Hem`i*bran"chi\, n. pl. [NL. See Hemi-, and
   Branchia.] (Zool.)
   An order of fishes having an incomplete or reduced branchial
   apparatus. It includes the sticklebacks, the flutemouths, and
   Fistularia.
   [1913 Webster]