formal
1
: causing or likely to cause damage or destruction
Smoking is ruinous [=(more commonly) dangerous, hazardous] to your health.
ruinous effects/consequences
2
: costing far too much money
ruinous price increases
3
chiefly British, formal
: falling apart : badly damaged
a ruinous building
The house has fallen into a ruinous state.
Cite this Entry
“Ruinous.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/ruinous. Accessed 20 Jun. 2026.
Copy Citation
