Green’s Dictionary of Slang

an unctuous bearing; flattering or toadying behaviour.

1937		H.C. Bailey Clunk’s Claimant 84: That smarm of holiness [...] was pretty near the ruddy limit [OED].
1982		P. Bailey Eng. Madam 99: Typical man, I thought – all smarm when he wants his oats.
1995		B. James Detective is Dead (1996) 41: No trial rigmarole. No QC smarm-bucket with his, ‘If you please, Detective Chief Superintendent.’.
1998		I. Welsh Filth 31: I then have to listen to his smarm about how good an officer I am.
2005		Ariano & Sternbergh Hey! It’s That Guy! 1991: Some actors are blessed with charm; Christopher McDonald is blessed with smarm [...] two parts country club, one part used-care salesman, and one part Caesar’s Palace.