A stickleback is a small fish which has sharp points along its back.
stickleback in British English
(ˈstɪkəlˌbæk)
noun
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
Word origin
C15: from Old English stickel prick, sting + back1
stickleback in American English
(ˈstɪkəlˌbæk)
noun
any of a family (Gasterosteidae, order Gasterosteiformes) of small, bony-plated,marine and freshwater bony fishes with two to eleven sharp spines in front of the dorsal fin: the male builds a nest for the female's eggs
Word origin
ME stykylbak < OE sticel, a prick, sting < base of sticca (see stick) + ME bak, back1