abackEnglishOxford Dictionary of Englishaback /əˈbak / ▸ adverb 1 archaic towards or situated to the rear; back: the little strip of pasture aback of the house. 2 Sailing with the sail pressed backwards against the mast by a headwind: Peter holds the jib aback until our bow swings across the wind. – PHRASES take someone aback shock or surprise someone: he was taken aback by her directness.– ORIGIN Old English on bæc(see a-2, back). The term came to be treated as a single word in nautical use.