adjective
Of an animal: having feet which are naturally flat; (specifically) of a horse: having hoofs with soles close to the ground.
Of a person: having the physical condition of flat feet (“a condition where the soles of the feet are in full contact with the ground, either because the arches have collapsed or because they never developed”).
(by extension) Of a thing (especially (rail transport) a rail): having a flat base; flat-bottomed.
Blunt and unsubtle; lacking finesse; clumsy.
Unprepared, unready.
Direct, downright, straightforward; also, holding firmly to and maintaining a decision; standing one's ground.
verb
simple past and past participle of flat-foot.