Wiktionary
adv. To an unnerve degree
Usage examples of "unnervingly".
The weather remained unnervingly warm, and toward mid-morning, as the pies came out of the oven, the rest of the Elves and their guests carpooled in.
The process was unnervingly rapid, like watching a party balloon inflate into the shape of an animal.
They were barely close enough together to give him binocular vision--but, unnervingly, Aranimas didn't much bother with binocular vision.
It looked unnervingly like pastrami, but turned out to be, as Byars put it, 'the guid roast beef.
Several dozen military vehicles were drawn up along the side of the motorway, while a couple were speeding along the carbon concrete towards the unnervingly precise band of incinerated vegetation.
He sweated, recalling police, recalling that ominous line of military ships docked just outside these offices on blue dock, two carriers in port, no less, with troops, troops like Viking stationers, unnervingly alike in size and build and manner, the stamp of birth labs.