The Collaborative International Dictionary of English v.0.48:

back-to-back \back-to-back\ adj.
   1. occurring immediately one after the other; consecutive.
      back-to-back home runs

   Syn: consecutive.
        [WordNet 1.5]

   2. oriented with the backs toward each other, and sometimes
      touching.
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

back-to-back
    adj 1: one after the other; "back-to-back home runs" [syn:
           back-to-back, consecutive]