let loose

phrase

1

: to allow (someone or something) to move or go freely

He let the dogs loose in the courtyard.

cattle let loose to graze on the green fields

—often used figuratively

a director who's willing to let her actors loose to interpret their roles however they see fit

how to stop the violence that has been let loose on the city

2

: to produce (something, such as a cry) in a sudden and forceful way

The crowd let loose an enormous groan when the pass was intercepted.

She let loose (with) a scream.