Definition of grim-faced:
(adj) :
Dismal and gloomy, cold and forbidding.
(adj) :
Ghastly or sinister.
(adj) :
Rigid and unrelenting.
(adj) :
Disgusting; gross.
(n) :
(MLE, slang, probably a fashionable word around 2006, now dated) A promiscuous woman.
(v) :
(transitive, rare) To make grim; to give a stern or forbidding aspect to.