To be taken aback means to be suddenly surprised or shocked by something unexpected, usually in a way that leaves you momentarily speechless or unsure how to react. When you're taken aback, something catches you so off guard that you need a moment to process what just happened.

Imagine working hard on a science project and expecting your teacher to point out problems, but instead she announces that you've won first place in the school competition. That startled, wide-eyed feeling of pleasant surprise means you've been taken aback. Or picture confidently answering a question in class, only to have your teacher gently explain that you're completely wrong. That stopped-in-your-tracks feeling is also being taken aback.

You might be taken aback by a friend's rude comment, by discovering your little brother cleaned his room without being asked, or by learning that your quiet classmate is a champion chess player. The phrase captures that brief frozen moment before you figure out how to respond.