flattie noun 13forms 1 noun13 •(informal) A flat white (a type of coffee). •(informal) A flatmate. •(Internet) A flat earther. •(informal) A flat pitch, which is typically easy to bat. •(informal) A Flat-coated Retriever. •(South-Africa) A flat marinated cut of meat. •(informal, offensive) A woman with very small breasts. •(informal) A flattie spider, generally in the family Selenopidae, so called because of its flattened, sprawling shape. •(informal) A navel that is neither protruding nor sunken. •(informal) A traditional two-dimensional motion picture, as opposed to a deepie. •(slang) The operator of a flat joint, or crooked gambling operation.A carnival hawker may run a legitimate game in which you have a fair chance to win, but then again he may be a flattie — a carnival grifter expert at separating the unwary from their money. — 1997 •(slang) A flat store. •A flat-bottomed sloop-rigged sharpie.This is the "flattie" model of this skiff — there was also a V-bottomed version similar to the m odified sharpie of Figure 6-4. — 1993 formsflatties