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."

Definitions of ruinous
  1. adjective
    extremely harmful; bringing physical or financial ruin
    “a ruinous course of action”
    synonyms: catastrophic
    causing or capable of causing harm
  2. adjective
    causing injury or blight; especially affecting with sudden violence or plague or ruin
    “a ruinous war”
    synonyms: blasting
    causing destruction or much damage
Word Family

Test prep from the experts

Boost your test score with programs developed by’s experts.

  • Proven methods: Learn faster, remember longer with our scientific approach.
  • Personalized plan: We customize your experience to maximize your learning.
  • Strategic studying: Focus on the words that are most crucial for success.


  • Number of words: 500+
  • Duration: 8 weeks or less
  • Time: 1 hour / week


  • Number of words: 500+
  • Duration: 10 weeks or less
  • Time: 1 hour / week


  • Number of words: 700+
  • Duration: 10 weeks
  • Time: 1 hour / week