The Collaborative International Dictionary
Heteracanth
Heteracanth \Het"er*a*canth\, a. [Hetero- + Gr. ? a spine.] (Zo["o]l.) Having the spines of the dorsal fin unsymmetrical, or thickened alternately on the right and left sides.
Wiktionary
heteracanth
a. (context zoology English) Having the spines of the dorsal fin asymmetrical, or thickened alternately on the right and left sides.