raise your eyebrows

raise your eyebrows (or an eyebrow)

show surprise, disbelief, or mild disapproval.
See also: eyebrow, raise

raise your ˈeyebrows (at something)

show, by the expression on your face, that you disapprove of or are surprised by something: Eyebrows were raised when he arrived at the wedding in jeans.When he said he was leaving, there were a lot of raised eyebrows.
See also: eyebrow, raise