Smooth and flattering; unctuously ingratiating; fulsome: a rather smarmy doctor and a highly officious nurse
Rich and sonorous; orotund and fruity; plummy: an announcer with a smarmy voice
Smug and self-righteous: Uncle Sam's Smarmy Look Into Employee Sex Lives
[1924+; origin unknown; since the earliest attested uses have to do with hair oil, it may be a vague blend of smooth, smear, palm oil, cream, etc]
The Dictionary of American Slang, Fourth Edition by Barbara Ann Kipfer, PhD. and Robert L. Chapman, Ph.D. Copyright (C) 2007 by HarperCollins Publishers. Cite This Source
Idioms and Phrases with smart-aleck
An impudent or obnoxiously self-assertive individual, a wise guy, as in New teachers often have a hard time coping with the smart alecks in their classes. This expression, dating from the mid-1800s, probably alluded to a person of this description who was named Alec or Alexander, but his identity has been lost.