Welcome to our blog.
Today our idiom is, snap at.
This means to quickly say a nasty remark and is usually done when the person is irritated for whatever reason.
Example 1
She snapped at me when I told her clean up her mess. She told me to mind "my own business".
Example 2
A. Where are the extra pens?
B. Don't you know? You've been working here for 3 years.
A. Don't snap at me. I just asked you a simple question.