Definition of pestiferously in US English:

pestiferously

adverb

  • In a pestiferous manner; (figurative) dangerously.

Origin

Late 16th century; earliest use found in John Foxe (?1517–1587), martyrologist. From pestiferous + -ly.

Pronunciation

pestiferously

/pɛˈstɪf(ə)rəsli/