something that is no longer relevant
Examples:
- All of the negotiations are finally water under the bridge. I am so glad we got the signed contract.
- The old disagreements they had are just water under the bridge. They are still close friends.
- It's all water under the bridge now — let's move on.
- The earlier dispute between the two firms is water under the bridge; they now work closely together.
Synonyms: in the past, bygones, history