all clear

WordReference Random House Learner's Dictionary of American English © 2025

ˈall ˈclear, n. [countable]

1. a signal that a danger has passed.
2. a signal to proceed:
   got the all clear to start the campaign.

WordReference Random House Unabridged Dictionary of American English © 2025

all′ clear′, 

1. the signal that an air raid or other danger is over.

• 1915–20

Collins Concise English Dictionary © HarperCollins Publishers::

all clear noun

1. a signal, usually a siren, indicating that some danger, such as an air raid, is over
2. an indication that obstacles are no longer present; permission to proceed