ru ‧ in ‧ ous /ˈruːənəs, ˈruːɪnəs/ BrE AmE adjective
1 . causing a lot of damage or problems:
a ruinous civil war
2 . costing much more than you can afford:
ruinous rates of interest
3 . formal a building that is ruinous has been almost completely destroyed SYN ruined :
an old ruinous chapel
ruinous state/condition
the ruinous state of the city walls
—ruinously adverb :
ruinously expensive