əˈbak adverb
Etymology: Middle English abak, from Old English on bæc, from on on, at, towards + bæc back — more at on , back
1. archaic
a. : toward or to the back or rear : backward , back
all suddenly dismayed … he fled aback — Edmund Spenser
b. : in the rear : behind
2. : in a position to catch the wind upon the forward surface of a sail — usually used of a square sail or yard
the ship came up into the wind with all yards aback — H.A.Chippendale
3. : by surprise : unawares — used with preceding take
completely taken aback at the question