Contrary to fact or truth: false tales of bravery. Deliberately untrue: delivered false testimony under oath. Arising from mistaken ideas: false hopes of writing a successful novel. Intentionally deceptive: a suitcase with a false bottom; false promises. Not keeping faith; treacherous: a false friend. See Synonyms at faithless. Not genuine or real: false teeth; false documents. Erected temporarily, as for support during construction. Resembling but not accurately or properly designated as such: a false thaw in January; the false dawn peculiar to the tropics. Music Of incorrect pitch. Unwise; imprudent: Don't make a false move or I'll shoot. Computer Science Indicating one of two possible values taken by a variable in Boolean logic or a binary device. In a treacherous or faithless manner: play a person false.