Sea Horse Definition

Any of a genus (Hippocampus) of small, semitropical, marine bony fishes of the same family (Syngnathidae, order Gasterosteiformes) as the pipefishes, having a slender prehensile tail, plated body, and a head and foreparts somewhat suggestive of those of a horse: it normally swims in an upright position, and the male incubates the eggs in a pouch in his abdomen.

A mythical sea creature, half fish and half horse.