WordNet sense 1 (having no cogency or legal force):

invalid, invalid

WordNet sense 2 (not according with the facts):

untrue

WordNet sense 3 (plausible but false):

specious, spurious

WordNet sense 4 (intentionally untrue):

mendacious

WordNet sense 5 (deliberately deceptive):

hollow

WordNet sense 6 (inappropriate to reality or facts):

delusive

WordNet sense 7 (not realistic):

unrealistic

WordNet sense 8 (not genuine or real; being an imitation of the genuine article):

fake, imitation, simulated, faux

WordNet sense 9 (contrived by art rather than nature):

artificial, unreal

WordNet sense 10 (deceptive or fraudulent; disposed to cheat or defraud or deceive):

dishonest, dishonorable

WordNet sense 11 (adopted in order to deceive):

assumed, fictitious, fictive, sham, pretended, put on

WordNet sense 12 (not genuine; imitating something superior):

counterfeit, imitative

WordNet sense 13 (inaccurate in pitch):

off-key, sour

WordNet sense 14 (not in harmony):

inharmonious, unharmonious

WordNet sense 15 (arising from error):

mistaken

WordNet sense 16 (not correct; not in conformity with fact or truth):

incorrect, wrong

WordNet sense 17 (likely to change frequently often without apparent or cogent reason; variable):

inconstant

WordNet sense 18 (in a disloyal and faithless manner):

faithlessly, traitorously, treacherously, treasonably