To copulate. In old Russian the verb meant “to battle” and comes from a Slavic root meaning “to penetrate, to touch, to feel” (compare Bulgarian барам, Macedonian бара).
Приходит мужик домой, а там жена с любовником барается…
This guy comes home and finds his wife and her lover screwing…
(yucca cat @ ЖЖ, 05/2011)