Similar to the act of paper bagging. However, because the person being bagged cannot breath under the plastic bag opposed to the paper bag, he/she will suffocate as a result. The term is used to describe someone that is so ugly that you would have to kill them after intercourse.
Adam: Charlies' girlfriend is a real minger, he ought to be Plastic Bagging that bitch.
Placing ones knackers on an unconscious person's forehead or face for shits'n'giggles. Usually documented through photographic evidence to maximise victim's displeasure.