Wiktionary
a. (context informal English) rigid humourless.
Usage examples of "lockjawed".
Tongue-tied, lockjawed, he stared at her like a bird transfixed by a snake, hoping for some sign that it was all right, that he had done the right thing.
And the two adventurers felt a yearning for these shimmer-girls such as they had never felt for mortal woman, so that they could no more turn back than men wholly ensorcelled or stark lockjawed mad.
It was now possible to discern certain plainclothesmen, hard of eye, stern of visage who, lockjawed, strode through the crowds, superior and supremely confident.
Back thrusters engaged, he shook two lockjawed Hellcats from his legs and hopped himself over-a skirmish line of Odeons, twisting around as he landed to bring the suit's chest-mounted impact cannon into play.
She spoke in the chirpy, lockjawed accents of a young Katharine Hepburn.