False, something not true.

Dictionary.com says:
false ( P ) Pronunciation Key (fôls)
adj. fals·er, fals·est
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.