Definition of flathead
1 (Flathead) a member of certain North American Indian peoples such as the Chinook, Choctaw, and Salish, named from their supposed practice of flattening their children’s heads artificially. the Salishan language spoken by those people. 2 informal a foolish person. 3an edible tropical marine fish that has a pointed flattened head with the eyes positioned on the top, typically burrowing in the seabed with just the eyes showing.
- Family Platycephalidae: several genera and species
4US (of an engine) having the valves and spark plugs in the cylinder block rather than the cylinder head, which is essentially a flat plate. (of a vehicle) having a flathead engine. 5 [as modifier] US (of a screw) countersunk.