Vaginal or anal intercourse.
We went down to the derelict casino where we came across Billyboy and his four droogs (friends); they were getting ready to perform a bit of the old in-out-in-out on a weepy young devotchka (girl) they had there - from the 1971 film "A Clockwork Orange"
by Anthony Brancato April 21, 2003
english slang term for sex, publicized in the movie clockwork orange
...so me and the other droogs were gettin ready for some of the 'ol in-out, in-out
by poosmack October 13, 2003