Stickleback

noun

1. Any of various small freshwater and marine fishes of the family Gasterosteidae, having erectile spines along the back.
2. Any fish of the family Gasterosteidæ: so called from the sharp spines of the back.
3. Any one of numerous species of small fishes of the genus Gasterosteus and allied genera. The back is armed with two or more sharp spines. They inhabit both salt and brackish water, and construct curious nests. Called also sticklebag, sharpling, and prickleback.
4. Any one of numerous species of small fishes of the genus Gasterosteus and allied genera. The back is armed with two or more sharp spines. They inhabit both salt and brackish water, and construct curious nests.
5. small (2-4 inches) pugnacious mostly scaleless spiny-backed fishes of northern fresh and littoral waters having elaborate courtship; subjects of much research