1.
back to back; standing with backs touching
The physical position of two people standing or sitting with their backs against each other.
2.
inseparably linked; two sides of the same coin
Figuratively describes two things that are closely connected, especially when something positive is inseparably linked with something negative or risky.
Literally "backs together" — from 背中 (back) + 合わせ (together). The literal sense describes the physical position, while the figurative sense expresses the idea that two contrasting things are inseparably connected, like two sides of the same coin.
Usage
As a physical description (sense 1), it is used with に as an adverb: 背中合わせに立つ. In the figurative sense (sense 2), it typically functions as a predicate: AとBは背中合わせだ.
Common collocations
- 背中合わせに立つ — to stand back to back
- 背中合わせに座る — to sit back to back
- 背中合わせの関係 — an inseparable relationship