1: An unfortunate clip of the testicles, usually at a tangent - which sometimes feels more painful than a full impact.

2: Something that is really funny

when you're hungover as shit after a spending a night drunk as a skunk

Used to describe a scene of banter that is so fucking hilarious that you acquire crease marks on your belly from laughing so hard. Often, recipients of a creaser will be left crying and/or on the floor. It can also be used when a very dead joke is made, and someone could sarcastically exclaim that it was a “creaser”.