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A signal, usually by siren, that an air raid is over or a danger has passed.
1. (Military) 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: he received the all clear on the plan.
the signal that a danger is over.
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|Noun||1.||all clear - a signal (usually a siren) that danger is over|
|2.||all clear - permission to proceed because obstacles have been removed|
permission - approval to do something; "he asked permission to leave"