Back to back means with backs touching, facing away. Stand back to back, back to back houses.
It also means one immediately after another, so two meetings can be back to back. Back to back houses were built sharing a rear wall, and whole cities of them were cleared in the last century.
1phraseback to backWith backs touching, facing away.
“They stood back to back to see who was taller.”
back to back is a phrase.
Practised in Directions & Position