WordNet sense 1 (unpleasantly and excessively suave or ingratiating in manner or speech):

buttery, fulsome, oily, smarmy, soapy, unctuous

WordNet sense 2 (lacking sincerity):

insincere

WordNet sense 3 (containing an unusual amount of grease or oil):

greasy, sebaceous

WordNet sense 4 (containing or composed of fat):

fat, fatty