aback
Concise Oxford English Dictionary © 2008 Oxford University Press:
aback/əˈbak/
▶adverb
- 1 archaic towards or situated to the rear.
- 2 Sailing with the sail pressed back against the mast by a headwind.
– phrases
take someone aback shock or surprise someone.
take someone aback shock or surprise someone.
'aback' also found in these Oxford entries:

