Gape-mouthed

"You may be wise in your study in the morning,” (says brow-beating Johnson, to his gape-mouthed admirer Boswell,) “ and gay in company at a tavern in the evening.”

Source: wiktionary

This argument also does Sweden, her king, and Chancellor Oxenstierna a regrettable historical injustice, for it trivializes the gape-mouthed surprise with which most European statesmen greeted the initial successes of the Swedish invaders in 1631.

Source: wiktionary

The brain, we are to understand, is sufficiently complex to supoprt higher functions because it is composed of some 10,000,000,000 neurons; and, as if this were not sufficient to leave one gape-mouthed with uncritical awe, it is pointed out that each of these components connects with numerous other components, so that the possible number of sub-units or combinations exceeds the number of atoms in the universe.

Source: wiktionary

Finally there were the fugitive images that imprinted themselves on his fizzling, fading brain as his gape-mouthed head spun in the air: a night sky flocked with gentle clouds; the saffron glow of the lamps along the riverbank; the door to the synagogue garret, flapping open in the breeze.

Source: wiktionary