When you have a sweaty ball sack, and you slap someone in the forehead with it so the sweat splashes all over their face.
Also can be a term for aftershave for your Balls
"Dude he was the first one to fall asleep, so i totally gave him a Webo Splash"
"This hoe would not shut up, so i Webo Splashed her, and finally she shut the hell up"
"My girl loves the smell of my balls after i use Webo Splash"