Merriam-Webster's Word Central

May 11, 2012

aback (adverb): \uh-BAK\
What does it mean?: : by surprise : unawares
How do you use it?: My entire family was taken aback by the news that, just one week before his wedding, cousin Daryl decided to elope with his fiancée instead.
Are you a word wiz?: "Aback" is a great word to add to your vocabulary, but you need to use it properly. Which sentence below uses "aback" correctly?

A. Mrs. Terry was taken aback by her neighbor's generosity.

B. How aback James felt when he heard his dog ran away.

C. Her aback leg itched underneath the cast.

D. We took the aback way, away from the road and through the woods.

"Aback" is an adverb. In modern English it usually modifies a form of the verb "take," as in response A, where Mrs. Terry was clearly surprised by her neighbor's generosity. Answers B, C, and D all use "aback" incorrectly, either as the wrong part of speech or with the wrong meaning. By the way, the word "back" would be a better choice for sentence D today, but back in the year 1000, you might have used "aback" as a synonym of "back" (although "aback" hasn't been used that way since at least the 1800s).