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ruinous

American  
[roo-uh-nuhs] / ˈru ə nəs /

adjective

  1. bringing or tending to bring ruin; destructive; disastrous.

    a ruinous war.

    Synonyms:
    catastrophic, devastating, calamitous
  2. fallen into ruin; dilapidated.

    a ruinous house.

  3. consisting of ruins.

    a ruinous city from antiquity.


ruinous British  
/ ˈruːɪnəs /

adjective

  1. causing, tending to cause, or characterized by ruin or destruction

    a ruinous course of action

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Word Forms

Etymology

Origin of ruinous

1350–1400; Middle English ruynouse < Latin ruīnōsus, equivalent to ruīn ( a ) ruin + -ōsus -ous

Explanation

Something ruinous is really terrible or devastating, like a ruinous hurricane that floods your house or the ruinous effect of a new law on a country's poorest citizens. The adjective ruinous perfectly describes something so bad that it truly causes ruin, "the destruction or disintegration of something." A house fire can be ruinous, and so can a bad hand at a poker table, if the player has bet her last dollar. Ruinous and ruin comes from the Latin root ruina, "a collapse, a rushing down, a tumbling down."

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Vocabulary lists containing ruinous

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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That’s how fast it is supposed to be able to grow without stoking ruinous inflation.

From MarketWatch Feb. 20, 2026