Usually applied when someone is being a fucker, fucking, or just the plain fuck.
It can be used as a verb, describing the action.
"Hey yo man, don't be such a maple-leafer!''
"Imma maple-leaf that bitch, cuz she stole may cookies."
Man 1 - "What is Mark doing?"
Man 2 - "Oh nothing. Just maple-leafing that hot chick from the bar!"
Man 1 - "Nice!"