Winking
Winking was a facial expression made by closing one eye, often as a sign of signaling shared hidden knowledge or intention.

In 2374, Quark had a conversation with Julian Bashir about what Jadzia Dax did, for instance, "sometimes she walks past the Infirmary and all she has to do is wink and somehow that makes my whole day look a little brighter." ()

External link 
 

Physiology