slack-jawed

With the mouth in an open position and the jaw hanging loosely, especially as indicating bewilderment or astonishment.

For one frightful moment there was no sound; even the men's breathing was hushed, and they sat slack-jawed, stunned, half-minded to believe this some hideous, incredible jest.

The Pudgelys and the Pinkhearts and the Roundasses are all staring at her, slackjawed.

Unsophisticated or unthinking; dimwitted in appearance.

She brought to the stage the barefoot, slack-jawed frontiersmen found on postcards in every convenience store and tourist trap in the Ozarks.

But driving a car—particularly the supersize models—really should demand more concentration than, say, slouching slack-jawed in front of the wide screen in your den.

Overly talkative; indiscreet.

As a matter of fact, it was by trying to lean on it that Spencer Clay got hold of the facts of the case; and when young Clay got hold of anything, Marois Bay at large had it hot and fresh a few hours later; for Spencer was one of those slack-jawed youths who are constitutionally incapable of preserving a secret.