not bat an eyelid idiom UK (US not bat an eye/eyelash)
眼睛都不眨一下;面不改色
to show no sign of surprise or worry when something unexpected happens
She told him she'd spent all her savings but he didn't bat an eyelid. 她告诉他已经花完了自己全部的积蓄，可他根本不为所动。