Definition of fallacious in English:



  • Based on a mistaken belief.

    ‘fallacious arguments’
    • ‘The utterly fallacious idea at the heart of the pro-war argument is that it is the duty of the anti-war argument to provide an alternative to war.’
    • ‘As this magazine reluctantly pointed out at the time, it is based on a fallacious theory that the brain works in strict hierarchical order: that the midbrain develops before the cortex.’
    • ‘Now that I have covered his central arguments as fallacious, I would like to step back and look at the work as a whole.’
    • ‘I think this is an entirely fallacious argument, with little to no factual support.’
    • ‘However, a careful examination of the proposed agreement exposes this argument as fallacious.’
    • ‘However, most of his evidence is in the form of specious and fallacious arguments.’
    • ‘We believe that argument to be absurd and fallacious, and hope that defenders of liberty will recognise that it is exactly this kind of panic-stricken measure that will most gratify the killers.’
    • ‘Alex is hawk-eyed when it comes to spotting lazy reasoning or fallacious argument, and lightning-fast at exposing it where it occurs.’
    • ‘It is also a fallacious argument that heavy vehicles alone account for the recurring accidents.’
    • ‘Some of Descartes' claims were fallacious such as his belief that the velocity of light is infinite.’
    • ‘If you stop to think about it, this argument is totally fallacious.’
    • ‘Nonetheless, he has worked his way to becoming a committed supporter of free trade; and, in the two books we have here to consider, he refutes a large number of fallacious arguments in favor of trade restrictions.’
    • ‘This argument is simply fallacious as both purposes can simultaneously apply.’
    • ‘Subscribers and practitioners of these fallacious beliefs were deemed at the time to be ‘properly schooled in science.’’
    • ‘The important things about being skeptical are therefore understanding rational argument and understanding fallacious and fraudulent argument.…’
    • ‘Speculation that MMR could be replaced by a series of individual vaccines was based on fallacious reasoning and would return Britain to the ‘dark ages’, he said.’
    • ‘As ever the Telegraph is busy fulmigating against so many straw men and other fallacious arguments.’
    • ‘The proofs are anecdotal or based on fallacious reasoning such as thinking that a correlation proves a causal connection.’
    • ‘SIR - The campaign to save and restore the Odeon has been widely supported, but despite this, Bradford Centre Regeneration has advanced fallacious arguments that the scheme would prove too costly.’
    • ‘Both the settlers and the far left believed that the disengagement could not take place because each group was gripped by a fallacious belief system, in which contradiction or dissent was impossible.’
    erroneous, false, untrue, wrong, incorrect, faulty, flawed, inaccurate, inexact, imprecise, mistaken, misinformed, misguided, misleading, deceptive, delusive, delusory, illusory, sophistic, specious, fictitious, spurious, fabricated, distorted, made up, trumped up
    baseless, groundless, unfounded, foundationless, unsubstantiated, unproven, unsupported, uncorroborated, ill-founded, without basis, without foundation
    bogus, phoney, iffy, dicey, full of holes
    View synonyms


Early 16th century: from Old French fallacieux, from Latin fallaciosus, from fallacia (see fallacy).