A lesbian term used to pick up on young, strait or possibly bi women. Women whom usually use this term are older women, normally picking up on young-teenage girl.
Mainly used at concert settings.
It means to perform in lesbian sex, for it is similar to two "walls" slamming into one another.
COUGAR: Honey, do you need to be front-walled?
UNSUSPECTING TEEN: I don't know, do I?