1. To crease or wrinkle something. A noun or pronoun can be used between "crinkle" and "up." Kathryn crinkled up her nose when she heard what I was making for dinner. Please don't put that document in the bag without a folder—you'll crinkle it up.

2. To become creased or wrinkled. I've been sitting for so long in my suit that the pants are crinkling up.