1. double over bend over or curl up, usually with laughter or pain
  2. double-decker a vehicle carrying many passengers
  3. double dagger a character used in printing to indicate a cross reference or footnote
  4. double-dealer a person who says one thing and does another
  5. double dipper someone who draws two incomes from the government
  6. double door two vertical doors that meet in the middle of the door frame when closed
  7. doubletree a crossbar on a wagon or carriage to which two whiffletrees are attached in order to harness two horses abreast
  8. double feature two games instead of one
  9. double boiler two saucepans, one fitting inside the other
  10. doubleheader two games played back-to-back
  11. double reverse (American football) a running play in which a first reverse is followed by a second reverse
  12. dappled-grey grey with a mottled pattern of darker grey markings
  13. double take a delayed reaction indicating surprise
  14. double time a fast marching pace (180 steps/min) or slow jog
  15. double star a system of two stars that revolve around each other under their mutual gravitation
  16. double date a date in which two couples participate
  17. double-dyed without qualification; used informally as intensifiers
  18. double bar notation marking the end of principal parts of a musical composition; two adjacent bar lines
  19. double-date go out on a date with a partner and another couple
  20. holdover something that has survived from the past