FreeVocabulary
Pernicious
/pərˈnɪʃəs/ adjective hardCausing gradual, often unnoticed harm; insidiously destructive.
The pernicious effects of the rumor spread quietly through the office for months before anyone noticed.
Memory Trick
From Latin 'nex,' meaning death or destruction (as in 'internecine') — pernicious things do lasting damage, often while going unnoticed.