pucker

Concise Oxford English Dictionary © 2008 Oxford University Press:
pucker/ˈpʌkə(r)/

▶verb tightly gather or contract into wrinkles or small folds. ▶noun a wrinkle or small fold.

– derivatives
puckery adjective.

– origin C16: prob. frequentative, from the base of poke2 and pocket (suggesting the formation of small purse-like gatherings).