porcupine fish

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of various tropical marine fishes of the family Diodontidae, having strong sharp spines on the body and capable of inflating themselves when attacked.

from The Century Dictionary.

• noun A diodontoid fish, as Diodon hystrix, whose skin is studded with prickles; a sea-porcupine. The various species inhabit tropical seas. See Diodontidæ, and cuts under Diodon and swell-fish.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun spines become erect when the body is inflated; worldwide in warm waters
• noun spines become erect when the body is inflated; worldwide in warm waters