1. be startled or astonished by somebody or something
I was a bit taken aback by what he/she said
'Aback' means in a backwards direction, so to be 'taken aback' implies that you were so surprised or shocked by somebody or something that you jumped back. It is usually used figuratively, and in relation to something somebody has said or done, or a sudden turn of events that catches you off guard and leaves you uncertain of how to respond for a short time. It can be used informally in both a social and professional context, and shares a similar meaning to the phrases 'lost for words,' and 'taken by surprise.'