- buttery, fulsome, oily, oleaginous, smarmy, unctuous - unpleasantly and excessively suave or ingratiating in manner or speech; "buttery praise"; "gave him a fulsome introduction"; "an oily sycophantic press agent"; "oleaginous hypocrisy"; "smarmy self-importance"; "the unctuous Uriah Heep"
Antonym: sincere (indirect, via insincere)