Taking a chill pill is a popular phrase that means to relax or calm down. However, there are many synonyms that can be used to express the same meaning in different ways. Some of these synonyms include, stay cool, mellow out, kick back, take a breather, and unwind. These words can be used interchangeably to convey the same message of taking it easy or taking a break from stress. Other synonyms for taking a chill pill could include, slow down, de-stress, decompress, or let loose. No matter which synonym is used, the message is clear: take a moment to relax and de-stress.