To crumple means to crush or squeeze something so it becomes wrinkled, creased, and smaller. When you crumple a piece of paper, you ball it up in your fist, turning a flat sheet into a wadded mess ready for the trash. A student might crumple up a failed drawing in frustration, or you might watch your carefully wrapped gift crumple when someone sits on it by accident.

The word captures both the action and the result: something that was smooth and structured becomes bent, folded, and compressed into an irregular shape. You can crumple aluminum foil, crumple a napkin, or watch a cardboard box slowly crumple under too much weight.

People can crumple too, though in a different way. When someone receives terrible news, you might see their face crumple as they struggle not to cry. A tired runner might crumple to the ground after crossing the finish line, their legs giving out beneath them. In these cases, the word suggests a sudden loss of structure or strength, like how paper loses its flatness when you squeeze it.

The opposite of crumple is to smooth or flatten something out, restoring its original shape.