heteracanth

Century Dictionary and Cyclopedia

1. In ichthyology having asymmetrical dorsal and anal fin-spines, alternately broader on one side than on the other; not homacanth.

Wiktionary

1. adj. zoology Having the spines of the dorsal fin asymmetrical, or thickened alternately on the right and left sides.

GNU Webster's 1913

1. adj. (Zoöl.) Having the spines of the dorsal fin unsymmetrical, or thickened alternately on the right and left sides.