To cock slap a person while said person is on the ground.
It's derived from a kid from California who was kicked out of high
school for sexual harassment. His last name was Wong. He was kicked out for sexually harassing
girls.
One
day during P.E. one kid was running and tripped. He fell to the ground. Wong came up to him, pulled out his cock, and cock slapped him. So "to wong someone" means to cock slap a person while that person is on the ground.