back' to back'
1. adjacent or contiguous but oppositely oriented; having the backs close together or adjoining: The seats in the day coach are back to back.
2. (of two similar events) following one immediately after the other; in unbroken sequence; consecutively: After losing all day, he picked winners back to back in the last two races.
3. Stud Poker.having a pair, consisting of the hole card and the first upcard: He had aces back to back.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.