Factum \Fac"tum\, n.; pl. {Facta}. [L. See {Fact}.] 1. (Law) A man's own act and deed; particularly: (a) (Civil Law) Anything stated and made certain. (b) (Testamentary Law) The due execution of a will, including everything necessary to its validity. 2. (Mach.) The product. See {Facient}, 2.