eye ‧ lid /ˈaɪlɪd/ BrE AmE noun [countable]
a piece of skin that covers your eye when it is closed:
His eyelids began to droop (=close, because he was sleepy) .
The room spun. Her eyelids fluttered (=moved up and down quickly) and she fainted.
⇨ not bat an eyelid at ↑ bat 2 (2)