1. The act or process of colliding; a crash or conflict.
2. Physics A brief dynamic event consisting of the close approach of two or more particles, such as atoms, resulting in an abrupt change of momentum or exchange of energy.
[Middle English, from Late Latin collsi, collsin-, from Latin collsus, past participle of colldere, to collide; see collide.]
Synonyms: collision, concussion, crash1, impact, jar2, jolt, shock1 These nouns denote violent forcible contact between two or more things: the midair collision of two light planes; the concussion caused by an explosion; a crash involving two cars; the impact of a sledgehammer on pilings; felt repeated jars as the train ground to a halt; a series of jolts as the baby carriage rolled down the steps; experienced the physical shock of a sudden fall.
collision /kln/ n. [C;U] 1 a crashing together: Two cars were involved in a collision.2to be on a collision course: a. to be headed toward crashing together: two cars on a collision courseb. to be headed for an argument or other conflict: The two politicians are on a collision course over raising taxes.