An ambiguous insult. It doesn't actually mean anything.

when you're hungover as shit after a spending a night drunk as a skunk

A random insult, perhaps born when someone misspelled biatch but still thought it sounded cool. Is still catchartic to the word user, but doesn't have the same degree of offense as the stem word.

or
A mix of biatch and the n-word, and in that case, the word user should really rethink their word choices unless used ironiclly