Green’s Dictionary of Slang

barse n.

[balls n. (1) + arse n. (1)]

1. (US campus) a consistent blunderer.

[US]Baker et al. CUSS 77: Barse A person who always does the wrong thing.

2. the perineum, i.e. the portion of flesh between the underside of the testes and the anus.

[UK]Roger’s Profanisaurus in Viz 87 Dec. n.p.: barse n. The perineum; that little bit between your balls and your arse.