Taken unawares or by surprise; in a state of unpreparedness.
Middle english abak, from old english on bæc; akin to old high german bah back and probably to old english bæc, bæce back.
- She was taken aback by his rude behavior.
- He was caught aback by the news.
- The proposal took her aback.
- The sudden noise caught me aback.
- The change in plans caught them aback.