from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To kiss passionately.
- n. A passionate kiss.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- v. touch with the lips or press the lips (against someone's mouth or other body part) as an expression of love, greeting, etc.
Possibly from the same roots as snug (meaning to lie close) which one has to do for a proper snog. (Wiktionary)