1. Disaster,calamity,catastrophe,cataclysm refer to adverse happenings often occurring suddenly and unexpectedly. A disaster may be caused by carelessness, negligence, bad judgment, or the like, or by natural forces, as a hurricane or flood: a railroad disaster.Calamity suggests great affliction, either personal or general; the emphasis is on the grief or sorrow caused: the calamity of losing a child.Catastrophe refers especially to the tragic outcome of a personal or public situation; the emphasis is on the destruction or irreplaceable loss: the catastrophe of a defeat in battle.Cataclysm, physically an earth-shaking change, refers to a personal or public upheaval of unparalleled violence: a cataclysm that turned his life in a new direction.
1590s, from Middle French désastre (1560s), from Italian disastro "ill-starred," from dis-, here merely pejorative (see dis-) + astro "star, planet," from Latin astrum, from Greek astron (see star (n.)). The sense is astrological, of a calamity blamed on an unfavorable position of a planet.