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
Weak and fallacious are semantically related. In some cases you can use "Weak" instead an adjective "Fallacious".
Weak
Weak adjective - Not using or following good reasoning.
Usage example: your argument is weak
Fallacious and weak are semantically related. Sometimes you can use "Fallacious" instead an adjective "Weak".
Mutual synonyms
Both words in one sentence
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When the opponent is using a fallacious Proof by Verbosity (aka the Gish Gallop); firing so many weak points off that it is impossible to respond to them within the format of the debate.
Source: Ad Hominem - Learn to spot weak or fallacious logic in the media around you.
Cite this Source
Weak and Fallacious. (2016). Retrieved 2026, August 14, from https://thesaurus.plus/related/fallacious/weak
Fallacious & Weak. N.p., 2016. Web. 14 Aug. 2026. <https://thesaurus.plus/related/fallacious/weak>.
Weak or Fallacious. 2016. Accessed August 14, 2026. https://thesaurus.plus/related/fallacious/weak.
Google Ngram Viewer shows how "fallacious" and "weak" have occurred on timeline