The "!" after the m is a sound made by pressing ones lips together and abruptly opening the mouth, making a popping noise.
The term is an onomatopoeia, used to imitate the sound of abrupt cessation of oral sex.
2. (Monged)- A vegetive state of mind/being usually effective after consuming large quantities of alcohol, weed, lsd, ecstacy etc or combinations of.
2. Steve's well monged after we spiked his drink with acid, muhahahaha.