Wiktionary
gobsmack
vb. (context transitive slang English) To astonish.
Usage examples of "gobsmack".
He loved Pascoe dearly, but it did his heart good to see those intelligent sensitive features gobsmacked from time to time.
He was, for a moment, gobsmacked by the sheer presumption of a mere student, twenty-one years old, with no degree, calling into question the great Boyle’.