Fallacious
Fallacious adjective - Not using or following good reasoning.
Usage example: it's fallacious to say that something must exist because science hasn't proven its nonexistence
Unreasonable is a synonym for fallacious in false topic. In some cases you can use "Unreasonable" instead an adjective "Fallacious", when it comes to topics like illogical.
Unreasonable
Unreasonable adjective - Having no basis in reason or fact.
Usage example: an unreasonable assumption
Fallacious is a synonym for unreasonable in illogical topic. You can use "Fallacious" instead an adjective "Unreasonable", if it concerns topics such as not logical or sensible.
Mutual synonyms
Related pairs
- improper and fallacious
- improper and unreasonable
- stupid and fallacious
- stupid and unreasonable
- wrong and fallacious
- wrong and unreasonable
- weak and fallacious
- weak and unreasonable
- inconsistent and fallacious
- inconsistent and unreasonable
- irrational and fallacious
- irrational and unreasonable
- invalid and fallacious
- invalid and unreasonable
Both words in one sentence
- Seeing a wet sidewalk and concluding that there was rain is fallacious—not deductively valid—but it is not necessarily false, nor is it necessarily an unreasonable inference to make.
Source: Logical Fallacies
Cite this Source
Unreasonable and Fallacious. (2016). Retrieved 2026, July 21, from https://thesaurus.plus/related/fallacious/unreasonable
Fallacious & Unreasonable. N.p., 2016. Web. 21 Jul. 2026. <https://thesaurus.plus/related/fallacious/unreasonable>.
Unreasonable or Fallacious. 2016. Accessed July 21, 2026. https://thesaurus.plus/related/fallacious/unreasonable.
Google Ngram Viewer shows how "fallacious" and "unreasonable" have occurred on timeline