a. [ L. ruinosus: cf. F. ruineux. See Ruin. ] 1. Causing, or tending to cause, ruin; destructive; baneful; pernicious; as, a ruinous project. [ 1913 Webster ] After a night of storm so ruinous. Milton. [ 1913 Webster ] 2. Characterized by ruin; ruined; dilapidated; as, an edifice, bridge, or wall in a ruinous state. [ 1913 Webster ] 3. Composed of, or consisting in, ruins. [ 1913 Webster ] Behold, Damascus . . . shall be a ruinous heap. Isa. xvii. 1. [ 1913 Webster ] Syn. -- Dilapidated; decayed; demolished; pernicious; destructive; baneful; wasteful; mischievous. [ 1913 Webster ] -- Ru"in*ous*ly adv. -- Ru"in*ous*ness, n. [ 1913 Webster ] | 