godan verb (-ru)
have sex; bang someone
Vulgar slang used mainly by men; equivalent to 'do it' or 'get laid'. Often implies a casual or one-night encounter.
昨日、彼女と一発やった。
I banged my girlfriend yesterday.
飲み会の後、あの子と一発やるつもりだ。
After the drinking party, I plan to have sex with that girl.