1 bad-tempered, spiteful (a vicious dog; vicious remarks).
2 violent, severe (a vicious attack).
3 of the nature of or addicted to vice.
4 (of language or reasoning etc.) faulty or unsound.
Phrases and idioms:
vicious circle see CIRCLE n. 11. vicious spiral continual harmful interaction of causes and effects, esp. as causing repeated rises in both prices and wages.
Derivatives:
viciously adv. viciousness n.
Etymology: ME f. OF vicious or L vitiosus f. vitium VICE(1)
Useful english dictionary. 2012.