nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A road signal for directing vehicular traffic by means of colored lights, typically red for stop, green for go, and yellow for proceed with caution. Also called stoplight, traffic signal.