Definitionen
1.VerbTo double the quantity, amount or duration of something"I'm going to double up my enlistment."
2.VerbTo double one's amount of chips by winning an all-in pot.
3.VerbTo bend, bend over; to fold; to stoop.
4.VerbTo cause (someone) to bend over; to beat up (someone)."I doubled him up with a swift punch to the stomach."
5.VerbTo have a secondary use."This unfolding sofa doubles up as a bed."
6.VerbTo get the second out in a double play, typically referring to getting an out by beating a runner back to a base (often by throwing) after a fly ball has been caught"Jones snared the liner and then stepped on the bag to double up the runner."
7.VerbTo employ double the usual resources for a particular purpose; to work in pairs.
8.VerbTo marry or live with someone; to share a living space.