ocean sunfish

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

• noun A large marine fish (Mola mola) having an oval body with long dorsal and anal fins and a short tail, found in temperate and tropical seas worldwide.

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

• noun among the largest bony fish; pelagic fish having an oval compressed body with high dorsal and anal fins and caudal fin reduced to a rudder-like lobe; worldwide in warm waters