Tighten his jaw

What does someone exactly do, if he "tightens his jaw"?
The context is a lecture, the man giving the speech is quite tired of it already.

"He tightened his jaw, coughed and drew himself up one last time"

It is an indication that he is determined, resolute.

Replies

  • Tighten his jaw R. Berg 30/August/07
    • Tighten his jaw Smokey Stover 30/August/07