chill pill

Slang.

noun

something that has a calming or relaxing effect.

Idioms

    take a chill pill, (often used imperatively) to calm down; relax: Stop shouting! Take a chill pill!
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British Dictionary definitions for take a chill pill

chill pill

noun

informal an imaginary medicinal pill with a calming, relaxing effecttake a chill pill

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012