double

Concise Oxford English Dictionary © 2008 Oxford University Press:
double/ˈdʌbl/

▶adjective

• 1 consisting of two equal, identical, or similar parts or things: double doors.

  ■ having two different roles or interpretations.

  ■ (of a flower) having more than one circle of petals.

  ■ (of a domino) having the same number of pips on each half.

• 2 having twice the usual size, quantity, or strength: a double brandy.

• 3 designed to be used by two people.

• 4 Music lower in pitch by an octave.

▶predeterminer twice as much or as many. ▶adverb at or to twice the amount or extent. ▶noun

• 1 a thing which is twice as large as usual or is made up of two parts.

  ■ a system of betting in which the winnings from the first bet are transferred to a second.

  ■ Darts a hit on the ring enclosed by the two outer circles of a dartboard, scoring double.

  ■ Bridge a call that increases the penalty points for the defenders if the declarer fails to make the contract.

• 2 a person who looks exactly like another.

• 3 Brit. two sporting victories or championships in the same season, event, etc.

• 4 (doubles) a game involving sides made up of two players.

• 5 Bell-ringing a system of change-ringing using five bells, with two pairs changing places each time.

▶pronoun an amount twice as large as usual. ▶verb

• 1 make or become double.

  ■ (double up) share a room.

  ■ (double up) use the winnings from a bet as the stake for another bet.

  ■ Bridge call a double.

• 2 fold or bend over on itself.

  ■ (double up) bend over or curl up, typically with pain or mirth.

• 3 (double back) go back in the direction one has come.

• 4 (double (up) as) be used in or play another, different role.

• 5 Music add the same note in a higher or lower octave to (a note).

• 6 Snooker pot (a ball) by making it rebound off a cushion.

– phrases
at (or US on) the double very fast.
double or quits (or US nothing) a gamble to decide whether a debt should be doubled or cancelled.

– derivatives
doubleness noun,
doubler noun,
doubly adverb.

– origin ME: via OFr. from L. duplus (see duple).