A momster is something your mother can turn into when she flips her shit and freaks out at you. This normally happens when:
1) you
cut your own hair
2) you pierce yourself
3) when you
break something
4) when you accidently say something in
front of her that is more of a "friend remark"
or 5) when you accidently drop your guinea pig that she really loves to feed.
teenager: "hey
mom nice new computer charger" *poke* *crash* D= "umm....te-he-he-he..." *runs in room...followed by a
mom...*
Momster: "YOU %^&* TEENAGER touchin' on my effing charger!!!!! AHHHerrrrrrrHAhbdsfjdkjf..."
teenager: "0_o holy shit, my
mom just turned into a momster and flipped her shit.. "