From Longman Dictionary of Contemporary Englishsleep around phrasal verb informalSEX/HAVE SEX WITHto have sex with a lot of different people without having a serious relationship with any of them – used to show disapproval → sleep→ See Verb table
Examples from the Corpus
sleep around• I don't sleep around any more, not since I met Jack.• If you sleep around, you increase your risk of getting AIDS. 