A wink (closing one eye). Used as a noun and as a suru-verb (ウインクする). Often done as a signal or flirtatious gesture.
彼は冗談が通じたときにウインクをした。
He winked when his joke landed.
店員がウインクするのは演出で、お客に向けた合図だ。
A clerk winking is part of the act—a signal directed at the customer.
写真を撮る前に友達と目配せして、同時にウインクした。
Before taking the photo, I signaled to my friend and we winked at the same time.