(1) Small (2-4 inches) pugnacious mostly scaleless spiny-backed fishes of northern fresh and littoral waters having elaborate courtship; subjects of much research
WiktionaryText
Noun
Any one of numerous species of small fishes of the genusGasterosteus and allied genera. The back is armed with two or more sharpspines. They inhabit both salt and brackish water, and construct curious nests.