Girl who is always getting you down, can be a bitch, snob or just depressing. Can also be used as just a general term for girls that you want to insult. Also applicable to feminine emo males.
A phrase that existed prior to stompbox that means stombox. A stomp box, or a stompbox, is an electronic guitar pedal, that is usually an on or off button controlling a guitar effect, but can refer to one that adjusts in increments.