shack up (with someone)
1. To live with someone or stay at someone's house temporarily. We've been shacking up at my brother's place while our house is being renovated. Do you mind if I shack up with you for a while? My wife and I are going through a bit of a rough patch.
2. To be in a sexual relationship with someone; to live or reside with someone in a sexual relationship. A: "I haven't seen Beth in a while." B: "She's been shacking up with some hotshot lawyer she started dating a few weeks ago." My parents still disapprove of us shacking up together before we're married. They're a little old-fashioned that way.
1. Living or sharing accommodations with someone while having a (usually casual) sexual relationship with them. I haven't seen my sister in weeks. I hear she's shacked up with some guy from Oklahoma these days. I was shacked up for a while with a woman I met downtown, but I've been on my own for the last couple of months.
2. Temporarily sharing accommodations with someone. A: "Do you have a place to stay while you're in town for the wedding?" B: "Yeah, I'm shacked up with my brother and his fiancée for the weekend."