The AI-powered English dictionary
plural green lights
A traffic light in its green state (indicating that vehicles may proceed). examples
(idiomatic) Approval, or permission to proceed. quotations examples
And Crossrail's Class 345 Aventra fleet finally has the green light to carry passengers to Heathrow Airport, after the Office of Rail and Road granted approval for the European Train Control System (ETCS) Level 2 overlay system.
2020 May 20, “Network News: Class 345s finally able to serve Heathrow Airport”, in Rail, page 15
(slang) A go-ahead to commit a crime, specifically to carry out a hit on someone (i.e. to kill).