adverb

1. With one's back facing that of somebody else.

   “Stand back to back so that we can see which of you is taller.”

2. Consecutively; one after the other.

   “We can't watch these films back to back! That's just way too much for one night.”

Synonyms: dos a dos

noun

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

adjective

1. Sequential or consecutive.

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

2. With one's back facing that of somebody else.

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

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