Definition of "flatty"

(regional, slang) A flatfish.

(Australia, slang) A flathead (fish).

(slang) A flat tire/tyre.

(archaic, US, slang) A policeman.

(slang) A flathead V8 engine.

(slang) A hot rod fitted with a flathead V8 engine.

(slang) Alternative form of flattie (“operator of crooking gambling operation”)