- any of the small, pugnacious, spiny-backed fishes of the family Gasterosteidae, inhabiting northern fresh waters and sea inlets, the male of which builds and guards the nest.
- any small teleost fish of the family Gasterosteidae, such as Gasterosteus aculeatus (three-spined stickleback) of rivers and coastal regions and G. pungitius (ten-spined stickleback) confined to rivers. They have a series of spines along the back and occur in cold and temperate northern regions
