- pernicious [pər nish′əs]adj.[Fr pernicieux < L perniciosus < pernicies, destruction < pernecare, to kill < per, thoroughly + necare, to kill: see NECRO-]1. causing great injury, destruction, or ruin; fatal; deadly2. Rare wicked; evilperniciouslyadv.perniciousnessn.SYN.- PERNICIOUS applies to that which does great harm by insidiously undermining or weakening [pernicious anemia, a pernicious dogma ]; BANEFUL implies a harming by or as by poisoning [a baneful superstition ]; NOXIOUS refers to anything that is injurious to physical or mental health [noxious fumes ]; DELETERIOUS implies slower, less irreparable injury to the health [the deleterious effects of an unbalanced diet ]; DETRIMENTAL implies a causing of damage, loss, or disadvantage to something specified [his error was detrimental to our cause ] -ANT. HARMLESS, INNOCUOUS
English World dictionary. V. Neufeldt. 2014.