A smash; a crash; especially, a serious accident on a railway, as when one train runs into another.(noun)
The Century Dictionary (Public Domain)
Use "smash-up" in a sentence
"Director Sylvain White (Stomp the Yard) tries a smash-up of irreverent comedy and non-stop action, à la Lethal Weapon."
"I used to hunt squirrels in the woods between subdivisions there; carried a homemade fishing pole to the nearby creek's deepest pools; caught crawfish by turning over rocks in the shallows; rode my bike to a friend's house to play smash-up derby with model cars; and it's where I had to sneak past the local bully's house by cutting through his neighbor's back yard."
"Sooner or later he is going to break out, and then there's going to be a smash-up."