What does "back to back" mean?

Alternative form of back-to-back.

Back to back

Common synonyms include: as one, as one man, at opposite extremes, behind, behind the scenes, coactively.

adj, adv

adj, adv ·Rare ·Advanced level

Adjective

Adverb

1
With one's back facing that of somebody else. not-comparable
"Stand back to back so that we can see which of you is taller."
2
Consecutively; one after the other. not-comparable
"We can't watch these films back to back! That's just way too much for one night."

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