Mom NBT is an acronym which stands for May Or May Not Be True. It is used with sarcasm to describe an awkward, embarrassing, or strange situation that is actually true though you don't really want to admit it openly.
Mom NBT It's Friday night and I am home alone watching Hannah Montana.
Mom NBT I made out with a chick with a mustache last night.
Mom NBT I have no recollection of what happened last night.