two-up

Short definition from Wiktionary

Noun

1. 1
   A game of chance, played by betting on the outcome of two pennies thrown in the air.

Adjective

1. 1
   Having two document pages per printed page.

Adverb

1. 1
   With two people aboard.

Verb

1. 1
   To share a cell with someone in prison, especially in a one-person cell.