/ əˈgɑːst; NAmE əˈgæst/ adjective
[ not before noun ] aghast (at sth) filled with horror and surprise when you see or hear sth
SYN horrified :
Erica looked at him aghast.
He stood aghast at the sight of so much blood.
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WORD ORIGIN
late Middle English : past participle of the obsolete verb agast , gast frighten , from Old English gǣsten . The spelling with gh (originally Scots ) became general by about 1700, probably influenced by ghost ; compare with ghastly .