Snog

Snog is slang for to kiss lengthily, passionately or lustfully.
Found on http://www.probertencyclopaedia.com/browse/ZSC.HTM

snog

kiss
Found on http://www.noslang.com/dictionary/s/

Snog

If you are out on the pull you will know you are succeeding if you end up snogging someone of the opposite sex (or same sex for that matter!). It would probably be referred to as making out in American, or serious kissing!
Found on http://www.effingpot.com/slang.shtml
No exact match found