What is boo-yah'd?

When someone smashes a party drink on a fellow partyer, crushes the drink cup or can into to their cranium and then proceeds to scream boo yah'd!

Sally finishes her drink. She sees Ben.

Sally then crushes the drink on Ben's head and then screams boo yah'd!

Ben just got boo yah'd.

boo-yah'd - meme gif