chill pill definition by American Heritage Dictionary
noun SlangThe 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.
Something that calms nerves or induces relaxation.
chill pill - Phrases/Idioms
take a chill pill
To calm down; relax.