boxfish 
noun (plural same or boxfishes)
A tropical marine fish that has a shell of bony plates enclosing the body, from which spines project. Also called trunkfish.
- Family Ostraciontidae: numerous species.
- Like its relative the puffer fish, the boxfish propels itself by waving its dorsal fin (on top of its body) and its anal fin (on the bottom), and it steers primarily with its pectoral fins and tail fin.
- The marine boxfishes (Teleostei: Ostraciidae) are mostly shallow-water, tropical reef-dwelling fishes that have 2/3-3/4 of their bodies encased in rigid bony carapaces, which arc keeled with various protuberances.