| 3. | shack up, Slang.
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shack up (with (so)
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shack up
Sleep together or live in sexual intimacy without being married. For example, They had been dating for two months and then decided to shack up. [Slang; first half of 1900s]
Stay or reside with, as in I'm shacking up with my cousin till I find a place of my own. [Slang; first half of 1900s]