crumple

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To crush together or press into wrinkles; rumple.
• intransitive verb To cause to collapse.
• intransitive verb To become wrinkled.
• intransitive verb To collapse.
• noun An irregular fold, crease, or wrinkle.

from The Century Dictionary.

• noun That which is crumpled, shriveled, or pressed into wrinkles; an irregular fold or wrinkle.
• To make crooked; deform; distort into curves.
• To draw or press into irregular folds; rumple; wrinkle.
• To contract into wrinkles; shrink; shrivel.

from the GNU version of the Collaborative International Dictionary of English.

• intransitive verb To contract irregularly; to show wrinkles after being crushed together.
• transitive verb To draw or press into wrinkles or folds; to crush together; to rumple.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A crease, wrinkle, or irregular fold.
• verb transitive To rumple; to press into wrinkles by crushing together.
• verb transitive To cause to collapse.
• verb intransitive To become wrinkled.
• verb intransitive To collapse.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• verb become wrinkled or crumpled or creased
• verb fall apart
• verb to gather something into small wrinkles or folds
• verb fold or collapse