1. placid That is calm which is free from disturbance or agitation; in the physical sense, free from violent motion or action; in the mental or spiritual realm, free from excited or disturbing emotion or pas Synonyms: calm, collected, imperturbable, sedate, still, composed, peaceful, self-possessed, tranquil, cool, placid, serene, undisturbed, dispassionate, quiet, smooth, unruffled Antonyms: agitated, excited, frenzied, passionate, ruffled, violent, boisterous, fierce, furious, raging, stormy, wild, disturbed, frantic, heated, roused, turbulent, wrathful