Source : Webster's Revised Unabridged Dictionary (1913)

Abdominal \Ab*dom"i*nal\, n.; E. pl. {Abdominals}, L. pl.
   {Abdominales}.
   A fish of the group Abdominales.

Abdominales \Ab*dom`i*na"les\, n. pl. [NL., masc. pl.]
   (Zo["o]l.)
   A group including the greater part of fresh-water fishes, and
   many marine ones, having the ventral fins under the abdomen
   behind the pectorals.