Ruinous \Ru"in*ous\, a. [L. ruinosus: cf. F. ruineux. See Ruin.]

1. Causing, or tending to cause, ruin; destructive; baneful; pernicious; as, a ruinous project.

After a night of storm so ruinous. --Milton.

2. Characterized by ruin; ruined; dilapidated; as, an edifice, bridge, or wall in a ruinous state.

3. Composed of, or consisting in, ruins.

Behold, Damascus . . . shall be a ruinous heap. --Isa. xvii. 1.

Syn: Dilapidated; decayed; demolished; pernicious; destructive; baneful; wasteful; mischievous. -- Ru"in*ous*ly, adv. -- Ru"in*ous*ness, n.

Source: Webster's Revised Unabridged Dictionary (1913)