green light
1. verb To permit someone or something to proceed. Likened to the green light of a traffic signal. Do you think the production company will green light our film?
2. noun Permission to proceed with some action or task. We're just waiting to get the green light from our managers before we release the latest software update.
green light, the
Permission to go ahead, as in The chief gave us the green light for starting this project. This term originated in the late 1800s for the signal used by railroads to indicate that a train could proceed. It was transferred to more general use in the first half of the 1900s.