This is the 9295th most frequent Japanese word.
白目
"白目" refers to the white part of the eye or a comedic expression where one rolls their eyes upward showing mostly the whites.
In this sentence, '白目' (white of the eye) refers to the action of rolling one's eyes upward in surprise, exposing the whites of the eyes.
彼は驚きのあまり白目を向いた。
He rolled his eyes in utter surprise.
Here, '白目' symbolizes an expression of frustration or a blank look derived from the whites of the eyes being more apparent.
ゲームがうまくいかず、彼女は白目になった。
Failing in the game, she had a blank expression.
In this context, '白目' is metaphorically used to describe the humorous act of exaggerated eye-rolling in reaction to a silly joke.