The "Nasty Nelson"!
This term came from a person serving into the body (or paddle) of the unsuspecting doubles partner of the receiver which results in a point for the server due to interference rules. Coined by Scott Lipitz after Timothy Nelson, who was known for using this against unsuspecting opponents. This video below was done by Scott "Golden Boy" on an unsuspecting player while he was filming. Scott is a super nice guy and this was a friendly game.
Why is this done? If you hit an opponent or their paddle with the ball - the serving team gets the point! It's just like hitting the ball - it may be going out - but if a person or their paddle gets in the way of the flight - it's your point!
The Nasty Nelson tends to be done when an opponent is standing too close to the middle of the court, intentionally or unintentionally. (I personally have sent a number of errant serves off and hit a person. I didn't mean to - but I still took the point!)
When it is done when an opponent is standing off to the side (as in the video below) it is called "dirty pickleball". Not a way to win a point and be in good standing with fellow competitors. In the video, this was a friendly game of pickleball.
So BEWARE! Stand off to the side when a serve is taking place and be ready to move out of the way should a ball come ripping at you! And if in tournaments, you may see this used if you're standing too close to that middle... or if a point is desperately needed - yikes!