Noah Webster's New International Dictionary of the English Language

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

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

3. (a.) Composed of, or consisting in, ruins.