accident
ac.ci.dent \'ak-s*d-*nt, -s*-.dent\ n [ME, fr. MF, fr. L accident-, accidens nonessential quality, chance], fr. prp. of accidere to happen, fr. ad- + cadere to fall - more at CHANCE 1a: an event occurring by chance or from unknown causes 1b: lack of intention or necessity : CHANCE 1c: an unforeseen or unplanned event 2a: an unfortunate event resulting from carelessness, unawareness, ignorance, or unavoidable causes 2b: an unexpected happening causing loss or injury which is not due to any fault or misconduct on the part of the person injured but from the consequences of which he may be entitled to some legal relief 3: a nonessential property of an entity or circumstance 4: an irregularity of a surface (as of the moon)
Webster's English Dictionary