1. Of paper, fabric, or a similar material, to form into a ball. In this usage, a noun or pronoun can be used between "crumple" and "up." My first draft of the poem was so bad that I just crumpled it up and threw it in the trash can. You can't just keep crumpling up your shirts and throwing them back in the closet—use the hamper please!

2. To collapse. I hardly remember the end of the marathon because I crumpled up as soon as I crossed the finish line.