A fallacy in logical argumentation WordNet 3.0 & Open English WordNet

In logic and philosophy, a formal fallacy, deductive fallacy, logical fallacy or non sequitur is a pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic system, for example propositional logic. Wikipedia

Reasoning of invalid structure Wikipedia Disambiguation

deductive argument that is invalid due to faulty reasoning, regardless of the truthiness of the conclusion Wikidata

A pattern of reasoning which is always wrong, due to a flaw in the structure of the argument. Wiktionary

A fallacy; a clearly defined error in reasoning used to support or refute an argument, excluding simple unintended mistakes. Wiktionary

Clearly defined error in reasoning. Wiktionary (translation)