When two people eat an apple (Usually a Pink Lady) and kiss afterwards.
The popularity comes from the sweetening effect the apple has on both parties lips, as well as freshening of the breath.
"Do you fancy a Pink Lady babe, ready for some Apple Kisses?"
"Oh my god we had apple kisses it was so romantic!"
"He tasted so good when we apple kissed."
When two prolapsed anuses touch eachother.
Alice and I got very drunk and tried out some apple kissing last night.