a person who just can't do anything right. it is used because just like it is impossible to insert a penis into a flat wall, (flat walls have no vagina) it is impossible for a wall fucker to do anything right.

When you eat dirt for the first time and leave your family to build a shack in the woods

A word created after some dude on IRC from Singapore told us to "pls fuck the fucking wall and die" ... hence creating wallfucker.

Can be either used to insult someone or just a (friendly) greeting.

a couple who are dry humping/ making out in the club against a wall.
a couple who are dry humping/ making out in the middle of the club.
dancing against the back corner wall at The Loft in Itaewon, South Korea because to dance anywhere else would get you raped.