sleep around
To engage in sex with many different partners. The term has a derogatory connotation. Apparently they have an open relationship and don't mind when the other person sleeps around. I had a reputation for sleeping around in college, but they were just baseless rumors.
sleep around (with someone)
Inf. to have sex with several partners over time; to be promiscuous. They say she sleeps around with just anybody all the time. Yes, she sleeps around.
sleep around
Engage in sex promiscuously, as in Fortunately, no one mentioned that both of them had slept around in their younger days . [Colloquial; 1920s]
sleep around
v.1. To be sexually active with more than one partner: I'm surprised they're getting married, considering how much they both sleep around.
2. sleep around on To be sexually unfaithful to someone: I am certain my spouse is sleeping around on me.