the act of colliding; a coming violently into contact; crash

the collision of two airplanes.

a clash; conflict

a collision of purposes.

Physics . the meeting of particles or of bodies in which each exerts a force upon the other, causing the exchange of energy or momentum.

noun

blow , bump , butt , concussion , contact , crash , demolishment , destruction , dilapidation , encounter , fender bender * , head-on , hit , impact , jar , jolt , knock , percussion , pileup * , rap , ruin , shock , sideswipe , slam , smash , strike , thud , thump , wreck , accident , brunt , clash , clashing , crackup , encroachment , impingement , infringement , insurance , interference , pileup , renitency , retroaction , smash-up , smashup