Longman Dictionary of Contemporary English
Douglas Harper's Etymology Dictionary
Wiktionary
a. 1 (context of a person English) With the mouth in an open position and the jaw hanging loosely, especially as indicating bewilderment or astonishment. 2 (context idiomatic of a person English) unsophisticated or unthinking; dimwitted in appearance. 3 (context idiomatic dated of a person English) Overly talkative; indiscreet.
Usage examples of "slack-jawed".
And then Hala jerked back, and her feet left the ground in small levitating increments until Mathew stared up, slack-jawed, at the soles of her feet.
For the next few segs, they all stood slack-jawed as I gave the full, personally annotated lecture on individual weapons.
Andy Burne, Clint Kael and Al Vayre, all holding their patched-up rifles, staring in slack-jawed amazement at the tableau of scarlet death in front of them.
Look you, I have noticed in my long life that those who eternally break in upon Those Above with complaints and reports and bellowings and weepings are presently sent for in haste, as our Colonel used to send for slack-jawed down-country men who talked too much.
Even allowing for the fact that the boy was in a hypnotic trance, there was an expression of idiocy on his loose-lipped, slack-jawed face, a pervading dullness.
Once again, I was slack-jawed: The ghosts of I Am Not Spock had returned to haunt me againthis time in the form of the myth that I had been the one who wanted to kill the Vulcan.
Light shafted down through these patches across the awful fecund waters, and I thought of an ancient engraving, a phantasma of Earth's seas, filled with bat-finned, slack-jawed, many-eyed grotesques.
A string of drool that could swallow up every star we can see in the night sky connects the lips of his slack-jawed mouth.
The grunts were struck wide-eyed, slack-jawed and speechless and at least one track nearly drove off the swing bridge and into the water with shock.
When Phil Fabrizio ambles closer to my treads, head tipped back in a slack-jawed perusal of my prow, I track the movement with anti-personnel chain guns and remind him—sharply—to halt.