Oleaginous, unctuous (4)
I believe the answer is:
oily
I believe this is a double definition.
'oleaginous' is the first definition.
(synonyms)
'unctuous' is the second definition.
(I know that unctuous can be written as oily)
(Other definitions for oily that I've seen before include "Like a lot of fish" , "Unctuous" , "Smarmy" , "Unpleasantly ingratiating" , "Greasy - obsequious" .)