in·ci·dent (ĭnʹsĭ-dənt)n. 1. A definite and separate occurrence; an event. See Synonyms at occurrence. 2. A usually minor event or condition that is subordinate to another. 3. Something contingent on or related to something else. 4. An occurrence or event that interrupts normal procedure or precipitates a crisis: an international incident.adj. 1. Tending to arise or occur as a result or accompaniment: “There is a professional melancholy... incident to the occupation of a tailor” (Charles Lamb). 2. Related to or dependent on another thing. 3.Physics. Falling upon or striking a surface: incident radiation. [Middle English, from Old French, apt to happen, an incident, from Latin incidēns, incident- present participle of incidere, to happen : in-, on; see in-2 + cadere, to fall; See kad- in Indo-European Roots.]