water under the bridge
US /ˈwɔtər ˈʌndər ðə brɪdʒ/
UK /ˈwɔtər ˈʌndər ðə brɪdʒ/
1.
past events or issues that are no longer important or relevant, and should be forgotten
:
•
Their old argument is just water under the bridge now; they've moved on.
•
I know we had some disagreements, but that's all water under the bridge.