MEANING : 1. injurious, harmful or destructive
2. (archaic) evil, malicious or wicked
3. deadly or fatal
USAGE EXAMPLE 1 : The pernicious Tuberculosis virus is making a comeback and precautions have to be taken by the people against contracting this deadly disease.
USAGE EXAMPLE 2 : Apparently, Frum is unaware that TR declared, “Thank God I am not a free trader. Pernicious indulgence in the doctrine of free trade seems inevitably to produce fatty degeneration of the moral fibre.”