green light

From the standard red-green color scheme used in traffic lights and railway signals.

• Audio (AU)

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green light (plural green lights)

1. A traffic light in its green state (indicating that vehicles may proceed).

   The drive home was much faster than usual; somehow we managed to hit every green light.

2. (idiomatic) Approval, or permission to proceed.

   We have a green light on the project. Work starts today.

3. (slang) A go-ahead to commit a crime, specifically to carry out a hit on someone (i.e. to kill).

   Yo man, I heard someone had put a green light out on you, so watch your back.

• green arrow
• red light
• yellow light