adj. 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. 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. viciously adv. viciousness n.
[ ME f. OF vicious or L vitiosus f. vitium VICE(1) ]