Lewis & Short

horrĭfĭco, āvi, ātum, 1, v. a. [horrificus], to make rough or terrible, to cause terror (poet. and in post-Aug. prose): flatu placidum mare matutino Horrificans Zephyrus, ruffling, = crispans, Cat. 64, 271: ore ferarum Et rictu horrificant galeas, Sil. 3, 389: carcer, catenae, fuga, exsilium horrificaverant dignitatem, had made terrible, Flor. 3, 21, 10 Duk.: mentes, Claud. Bell. Get. 250.
Absol.: multaque praeterea vatum praedicta piorum Terribili monitu horrificant, cause horror, Verg. A. 4, 465.