double up

Short definition from Wiktionary

Verb

1. 1
   To double the quantity, amount or duration of something
2. 2
   To double one's amount of chips by winning an all-in pot.
3. 3
   To bend, bend over; to fold; to stoop.
4. 4
   To cause (someone) to bend over; to beat up (someone).
5. 5
   To have a secondary use.
6. 6
   To 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
7. 7
   To employ double the usual resources for a particular purpose; to work in pairs.
8. 8
   To marry or live with someone; to share a living space.