WordNet sense 1 (containing or based on a fallacy):

unsound

WordNet sense 2 (having no cogency or legal force):

invalid, invalid

WordNet sense 3 (intended to deceive):

deceitful, fraudulent

WordNet sense 4 (deceptive or fraudulent; disposed to cheat or defraud or deceive):

dishonest, dishonorable

WordNet sense 5 (not correct; not in conformity with fact or truth):

incorrect