let loose something
US /lɛt luːs ˈsʌmˌθɪŋ/
UK /lɛt luːs ˈsʌmˌθɪŋ/

1.
释放, 放开
to release something, often with force or without restraint
:
•
The dog was let loose in the park to run freely.
狗被放开在公园里自由奔跑。
•
He let loose a string of curses after hitting his thumb.
他撞到拇指后破口大骂。