- The definition of aghast is someone or something who has been surprised, awed or horrified.
An example of someone who might feel aghast is a person who returns home to find his house has burned down.
aghast definition by Webster's New World
Origin: Middle English agast, past participle of agasten, to terrify ; from a-, intensive plush gasten ; from Old English gaestan, to terrify ; from gast, ghost
aghast definition by American Heritage Dictionary
Origin: Middle English agast, past participle of agasten, to frighten : a-, intensive pref. (from Old English ā-) + gasten, to frighten (from Old English gǣstan, from gāst, ghost).