His jaw was going up and down as if he was trying to say something that wouldn't come.

Tyler's jaw had gone slack as he pulled back, looking down into her eyes.

My jaw went slack and the world lost focus for a moment.

People's jaws are going to hit the floor when they hear it.

I felt his jaw go and his body went slack.

Her eyes went wide and she felt her jaw go slack.

The outside jaw also goes all the way to the floor - or nearly so.

He started to say something, but suddenly his jaw went slack.

The sec man's jaw went slack, his face suddenly pale.

His jaw went to work like he was frustrated, not so much chewing as grinding.