1. adjective [usu ADJ n] If you describe the cost of something as ruinous, you mean that it costs far more money than you can afford or than is reasonable. ⇒ Many Britons will still fear the potentially ruinous costs of their legal system. ruinously
adverb [ADV adj] ⇒ ...a ruinously expensive court case. 2. graded adjective & adjective [usu ADJ n] A ruinous process or course of action is one that is likely to lead to ruin. ⇒ The economy of the state is experiencing the ruinous effects of the conflict. ruinously
adverb [usu ADV -ed] ⇒ ...cities ruinously choked by uncontrolled traffic.
COBUILD Advanced English Dictionary. Copyright © Harper Collins Publishers