back-to-back

• IPA^(key): /ˌbæk.təˈbæk/

back-to-back (not comparable)

1. Sequential or consecutive.

   Ruth and Gehrig hit back-to-back home runs.

   They sat through two back-to-back movies.

   • 2011 February 12, Les Roopanarine, “Birmingham 1 - 0 Stoke”, in BBC‎:

     An injury-time goal from Nikola Zigic against an obdurate Stoke side gave Birmingham back-to back Premier League wins for the first time in 14 months.

2. With one's back facing that of somebody else.
3. (physics, by extension) Emerging in exactly opposite directions.
   • 2009, R. Fiore; Alessandro Papa; Igor Ivanov; Jacques Soffer, Diffraction 2008: International Workshop on Diffraction in High Energy Physics, Amer Inst of Physics:

     Seen in laboratory frame the photon-jet pair is not any longer back-to-back and the energy balance is distorted.

   • 2000, S. Söldner-Rembold, Photon '99: Proceedings of the International Conference on the Structure and Interactions of the Photon, Including the 12th International Workshop on Photon-Photon Collisions, Freiburg, Germany, 23-27 May 1999:

     This produces two back-to-back jets of hadrons that dominate the inclusive high energy cross-section.

   • 2015, Thomas Schörner-Sadenius, The Large Hadron Collider: Harvest of Run 1, Springer, →ISBN, page 392:

     Photons at leading order are produced back-to-back with an associated parton with nearly identical transverse momenta.

   • 1992, David Shaw Brown, A Comparison of High Transverse Momentum Direct Photon and Neutral Pion Events in Negative Pion and Proton-nucleus Collisions at 31.5 GeV Center of Mass Energy:

     In the rest frame of the ${\displaystyle \pi ^{0}}$ the photons emerge back-to-back isotropically.

4. (of a house) Having a party wall at the rear,

   We lived in a row of back-to-back houses.

5. (poker slang) Synonym of wired (“being a pair in seven card stud with one face up and one face down”).

back-to-back (not comparable)

1. Alternative form of back to back
   • 2021 December 15, Paul Clifton, “There is nothing you can do”, in RAIL, number 946, page 37:

     A ScotRail Driver: [...] A good friend of mine overshot two stations back-to-back a couple of years ago. He tried to stop at one station and slid by it. Tried to stop at the next station. He slid by that, too.

back-to-back (plural back-to-backs)

1. A house with a party wall at the rear.