"Is Lockhart the smarmiest bloke you've ever met, or what?"
- Ron (CS13)
"Yeah, that's right, smarm up to him, Malfoy," said Ron scathingly.
- watching Draco Malfoy speaking to Viktor Krum (GF16)
Self-satisfied, conceited; ingratiating in an oily way.
Smarm originally meant to smear (especially in the sense of slicking down with something like hair cream or oil) (NSOED), but now is used mostly in the sense of behaving in an oily way - that is, with a lot of overdone flattery and deference. In the U.S. we'd say "suck up" rather than "smarm up".