A nickname usually given to perverts who want to have sex with anything they see. This includes inanimate objects, animals, plants. Gangbang pangs normally become overly aggressive with objects (similar to a gangbang).
KW: Hey did you see Michael Pang the other day?
JT: No, what happened?
JE: I saw him! He was humping a pole until it fell off!
JC: Wow! What a gangbang pang!
JE: The other day that weirdo started humping a cat from behind.
KW: Must have been a gangbang pang.