Noun | 1. | ![]() shark - any of numerous elongate mostly marine carnivorous fishes with heterocercal caudal fins and tough skin covered with small toothlike scales genus Sphyrna, Sphyrna - type genus of the Sphyrnidae smooth hammerhead, Sphyrna zygaena - fished for the hides and vitamin-rich liver smalleye hammerhead, Sphyrna tudes - fished for the hide and vitamin-rich liver bonnet shark, bonnethead, shovelhead, Sphyrna tiburo - small harmless hammerhead having a spade-shaped head; abundant in bays and estuaries |