I. ˌback-to-ˈback¹ adjective [only before noun]
happening one after another:
They have had five back-to-back wins.

[TahlilGaran] Dictionary of Contemporary English ▲

II. back-to-back² noun [countable] British English
a house in a row or terrace built with its back touching the back of the next row of houses

[TahlilGaran] Dictionary of Contemporary English ▲

back to back
each immediately following the other.
They were the first team to win three championships back to back.

Etymology: based on the literal meaning of back to back (= with your back pressed against another person's back)

[TahlilGaran] English Idioms Dictionary ▲

back-to-back
[mainly American]
back-to-back events happen one after the other.
He appeared in three back-to-back interviews on television last night.

His idea of a good time is to go to three French movies back-to-back.

[TahlilGaran] English Idioms Dictionary ▲

back-to-back
1. next to each other and touching backs
The students were sitting back-to-back as they did their exercises for the gym class.

2. something follows immediately after something else, two people touching backs
There were two back-to-back games today because of the rain last week.

[TahlilGaran] English Idioms Dictionary ▲

back to back
adv.
1. Immediately following.
The health clinic had back-to-back appointments for the new students during the first week of school.
2. Very close to, as if touching.
Sardines are always packed in the can back-to-back.
The bus was so full that people had to stand back-to-back.

[TahlilGaran] English Idioms Dictionary ▲