If you look blank, your face shows no feeling, understanding, or interest.
茫然的; 无表情的; 漠然的
A blank is a space which is left in a piece of writing or on a printed form for you to fill in particular information.
(表格等的) 空白处
Abbot looked blank. "I don't quite follow, sir."
阿博特一脸茫然,“我不太明白,先生。”