Entry 2 senses Webster, 1913 Perilous /pĕr'-əl-əs/ · Per·il·ous · IPA /ˈpɛɹ.ɪ.ləs/ 01 a. Full of, attended with, or involving, peril; dangerous; hazardous; as, a perilous undertaking. 1. Full of, attended with, or involving, peril; dangerous; hazardous; as, a perilous undertaking. “Infamous hills, and sandy, perilous wilds.” — Milton. 2. Daring; reckless; dangerous.[Obs.] “For I am perilous with knife in hand.” — Chaucer.