1. Literally, a befalling; an event that takes place without one's foresight or expectation; an undesigned, sudden, and unexpected event; chance; contingency; often, an undesigned and unforeseen occurrence of an afflictive or unfortunate character; a casualty; a mishap; as, to die by an accident. Of moving accidents by flood and field. (Shak) Thou cam'st not to thy place by accident: It is the very place god meant for thee. (Trench)
4. (Science: logic) a property or quality of a thing which is not essential to it, as whiteness in paper; an attribute. A quality or attribute in distinction from the substance, as sweetness, softness.