pucker

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

• intransitive verb To gather into small wrinkles or folds.
• intransitive verb To become gathered, contracted, and wrinkled.
• noun A wrinkle or wrinkled part, as in tightly stitched cloth.
• noun A facial expression in which the lips are tightly pulled together and pushed outward.
• noun A tart flavor that causes one's lips to pucker.

from The Century Dictionary.

• To draw up or contract into irregular folds or wrinkles; specifically, in sewing, to gather: often followed by up: as, to pucker cloth in sewing.
• To become irregularly ridged or wrinkled: as, his face puckered up into a smile; the mouth puckers on eating choke-cherries.
• noun A drawing or gathering into folds or wrinkles; an irregular folding or wrinkling; a collection of irregularly converging ridges or wrinkles.
• noun A state of flutter, agitation, or confusion.

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

• noun A fold; a wrinkle; a collection of folds.
• noun Prov. Eng. & Colloq. U. S. A state of perplexity or anxiety; confusion; bother; agitation.
• verb To gather into small folds or wrinkles; to contract into ridges and furrows; to corrugate; -- often with up.

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

• verb To pinch or wrinkle; to squeeze inwardly, to dimple or fold.
• noun A fold or wrinkle.
• noun A state of perplexity or anxiety; confusion; bother; agitation.

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

• verb draw together into folds or puckers
• verb become wrinkled or drawn together
• noun an irregular fold in an otherwise even surface (as in cloth)
• verb to gather something into small wrinkles or folds