A sea fish with a huge, flat, round body that looks as if the back half has been cut off. It can grow to over two metres and is one of the heaviest bony fish in the world. People often see it lying on its side near the surface, as if it were sunbathing — one likely reason for the name; the round shape is another. It is harmless to people and eats mostly jellyfish. Careful, though: in American English "sunfish" is also the family name of some small freshwater fish in lakes and rivers, which people fish for. So the same word can mean a giant of the ocean or a little pond fish, depending on who is talking. The plural is usually sunfish, not sunfishes.