say it: uh-BAK
aback is an adverb meaning "having the wind against the forward side of the sails". It carries 2 recorded senses.
having the wind against the forward side of the sails
“the ship came up into the wind with all yards aback”
by surprise
“taken aback by the caustic remarks”
Definitions, synonyms and semantic relations for aback come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.