To go ape shit on, or attack, someone - all while screaming.
Only women can go banshee, as the phrase is based on the female spirit in Irish mythology that has a high-pitched scream/wail. Banshees are said to wail around a house if someone inside is about to die.
Originated in La Mesa, CA.
- "When I found some other bitch's underwear in Ben's closet, I totally went banshee on him."
- "Yeah, she didn't get the promotion. I'm kind of afraid she's gonna go banshee."