1. An old-fashioned word meaning to make out with someone, generally not heavily.
2. The practice of greedily eating or drinking something, i.e. "getting it down your neck"
"Me sister drank too much beer at the party and ended up dancing on the table."
"LOL the slapper
! How much beer DID she drink, then?"
"Must have had near fifteen. She was necking em like a sailor!!"