What is "grimacingly"

Usage examples of "grimacingly".

All eyes strained west—ahead, and it would have been hard to say which eyes glared the more madly, those of the fur-clad, grinningly white-toothed men, or those of long-faced, grimacingly white-toothed beasts.

She smiled grimacingly at Hank Szantho who returned her bril­liant, cold glare dully.