Per-nĭ'ciōus, a.

(-nĭsh'us), a. [Lat. perniciosus, from pernicies, destruction, from pernecare, to kill or slay completely, from the prefix per, thoroughly, and necare, to kill, slay, from nex, necis, a violent death; Fr. pernicieux, Pr. pernicios, Sp. & Pg. pernicioso, It. pernicioso, pernizioso.

1Sense 1. Having the quality of killing, destroying, or injuring: very injurious or mischievous; destructive. “Shot forth pernicious fire.” Milton. “The indulgence of his appetite to a degree most pernicious to his health.” Prescott.

2Sense 2. [Lat. pernix.] Quick. [Obs.] Milton.

Synonyms—Destructive; ruinous; deadly; noxious; injurious; hurtful; mischievous.