The term 'Broad Flat Fish' refers to a group of fish that have a wide, flat body shape. The most common type of broad flat fish is the RAY, which is a three-letter word in the crossword. RAYS are cartilaginous fish related to sharks and skates, and they typically have a flattened body and large pectoral fins. Another word for this type of fish is 'RAYS, ' which is a four-letter word in the crossword. Finally, the word 'SLAB' is also a four-letter word in the crossword, and it is another name for a broad flat fish.