(Multiple definition(s) word!)
Whack1: A onomatopoeia or sound effect when someone gets hit by another person/object.
Whack2: An excessive way to disrespect someone.
Whack 1: WHACK! She get's slapped across the face!
Whack 2: Wow dude! That shirt is completely whack!
A makeshift cutting or stabbing weapon, commonly manufactured clandestinely in a jail or prison using commonly available items or contraband. Also known as a shiv, shank, banger, etc. A term used in the Pennsylvania prisons.
Yo you better go hide that whack somewhere because I heard the CERT team is coming.