not bat an eye
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not bat an eyealso not bat an eyelid
to not show any reaction Mom didn't bat an eye when I told her I was getting married.
Usage notes: also used in the form without batting an eye with the same meaning: She can give a formal dinner for thirty without batting an eye.
not bat an eye/eyelash Informal
To show no emotion; appear unaffected: The reporter didn't bat an eyelash while reading the gruesome news.