- The definition of fallacious is something based on an erroneous or mistaken belief.
When you make an argument based on a mistaken belief, this is an example of an argument that would be described as fallacious.
- containing a fallacy; erroneous: fallacious reasoning
- misleading or deceptive
- causing disappointment; delusive
Origin of fallaciousClassical Latin fallaciosus
- Containing or based on a fallacy: a fallacious assumption.
- Tending to mislead; deceptive: fallacious testimony.
(comparative more fallacious, superlative most fallacious)
- Nouns often used with "fallacious": argument, reasoning, etc.