It sounded terrifyingly like a distant thunder of guns.
"My Attainment of the Pole"
Frederick A. Cook
You are terrifyingly clever; my intelligence is of the feeblest.
"Olivia in India"
O. Douglas
It was a smooth road, splendidly built, but steep and terrifyingly narrow-so narrow in places that it was nothing more than a shelf blasted from the sheer face of the cliff.
"Italy at War and the Allies in the West"
E. Alexander Powell