Thesaurus

Synonyms for Insincere include:

ambidextrous, artful, artificial, assumed, bad, base, beguiling, blackguardly, bogus, bootlicking, buttery, corrupt, counterfeit, crooked, deceitful, deceptive, dishonest, dishonorable, dishonourable, disingenuous, dissembling, dissimulating, dissimulative, distorted, double-dealing, double-faced, double-tongued, dreamed, duplicitous, envisioned, eye-deceiving, fabled, fabricated, fabulous, fake, fallacious, false, fancied, fanciful, fantastic, fantastical, fawning, feigned, fictional, fictitious, fictive, forged, fraudulent, fulsome, gilded, hallucinatory, hollow, hypocritical, illusional, illusionary, illusive, illusory, imaginary, imagined, imitative, inauthentic, incorrect, insincere, invented, Janus-faced, legendary, made-up, make-believe, mendacious, meretricious, misleading, misrepresented, mock, mythic, mythical, mythologic, mythological, notional, obsequious, oily, oleaginous, ostensible, ostensive, perverted, phoney, phony, picaresque, pictured, pinchbeck, plausible, pretend, pretended, pseudo, put on, rascally, roguish, scoundrelly, sham, shoddy, smarmy, soapy, specious, spurious, supernatural, sycophantic, synthetic, thieving, thievish, toadyish, trompe-l'oeil, trumped-up, twisted, two-faced, unauthentic, unctuous, unreal, unrealistic, untrue, untrustworthy, untrusty, visualised, visualized, wrong

insincere is a ADJ.