n.1 a violent impact of a moving body, esp. a vehicle or ship, with another or with a fixed object.
2 the clashing of opposed interests or considerations.
3 Physics the action of particles striking or coming together.
Phrases and idioms:
collision course a course or action that is bound to cause a collision or conflict.
Derivatives:
collisional adj.
Etymology: ME f. LL collisio (as COLLIDE)