To have sex to the rythem and beat of the music.
When a man's engorged member slides in and out of a womans disco hall. At the same time his shiny disco balls bang against her arse to the beat of the music being listened too and thus creating a wonderful melody of love making.
Person 1: How was last night?
Person 2: I had disco in my loins with this girl from the club. She loved it when the uptempo song came on as the beat was so fast but my disco balls feels like they have been in a boxing ring.