adjective

based on a mistaken belief.

fallacious arguments

erroneous,false,untrue,wrong,incorrect,faulty,flawed,inaccurate,inexact,imprecise,mistaken,misinformed,misguided,misleading,deceptive,delusive,delusory,illusory,sophistic,specious,fictitious,spurious,fabricated,distorted,made up,trumped up,baseless,groundless,unfounded,foundationless,unsubstantiated,unproven,unsupported,uncorroborated,ill-founded,without basis,without foundation,bogus,phoney,iffy,dicey,full of holes,(way) off beam,dodgy