1. a green-colored traffic light used to signal drivers, pedestrians, etc., that they may proceed.
2. authorization; approval; permission: The railroad has been given the green light on the proposed fare increase.
—v.t., -light•ed or -lit, -light•ing.
to give permission to proceed or authorization to (a project or person).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.