fallacious
adjective
fal·la·cious fə-ˈlā-shəs 
1
: embodying a fallacy
a fallacious conclusion
a fallacious argument
2
: tending to deceive or mislead : delusive
false and fallacious hopes
Conyers Middleton
Conyers Middleton fallaciously adverb
fallaciousness noun
Did you know?
Oh what a tangled web we weave / When first we practise to deceive! So wrote Sir Walter Scott in his 1808 poem Marmion. Scott’s line wasn't written with etymology in mind, but it might be applied to the history of "fallacious." That word traces back to the Latin verb fallere ("to deceive"), but it passed through a tangle of Latin and French forms before it eventually made its way into English in the early 1500s. Other descendants of "fallere" in English include "fail," "false," and "fault."
Synonyms
- illegitimate
- illogical
- inconsequent
- inconsequential
- invalid
- irrational
- nonrational
- unreasonable
- unreasoning
- unsound
- weak
See all Synonyms & Antonyms 
Example Sentences
it's fallacious to say that something must exist because science hasn't proven its nonexistence consumers who harbor the fallacious belief that credit-card spending will never catch up with them
Recent Examples on the Web The sense that this mandate imposed no cost was fallacious: the costs were hidden but effectively passed on to consumers in higher auto prices or shareholders in lower dividends. Michael Lynch, Forbes, 16 June 2022 The choice, the show asserted, feels less like a rational Court judgment and more like a fallacious argument that a fringe Facebook group might circulate as fact. Amanda Wicks, The Atlantic, 8 May 2022 The fallacious warning was likely amplified by YouTuber Bernard Hsu, known as Chubbyemu, who posted a lengthy dramatization of the case that has been viewed 1.5 million times. Beth Mole, Ars Technica, 28 Feb. 2022 Unfortunately, there’s a lot of contradicting and fallacious information floating around out there about how distance runners should and shouldn’t fuel to run fast. Outside Online, 12 Oct. 2020 Followers of QAnon also regularly show up at events and successfully spread new fallacious claims. New York Times, 20 Dec. 2021 Cannabis as a gateway drug seems to be a hypothesis based on simplistic and fallacious logical processes. Dario Sabaghi, Forbes, 7 Dec. 2021 But this is based on the fallacious notion that depletion of the resource means ever-higher prices. Michael Lynch, Forbes, 5 Nov. 2021 The thinking that dominates the institution is fundamentally fallacious. Steve Forbes, Forbes, 16 Sep. 2021 See More
Michael Lynch, Forbes, 16 June 2022 The choice, the show asserted, feels less like a rational Court judgment and more like a fallacious argument that a fringe Facebook group might circulate as fact. Amanda Wicks, The Atlantic, 8 May 2022 The fallacious warning was likely amplified by YouTuber Bernard Hsu, known as Chubbyemu, who posted a lengthy dramatization of the case that has been viewed 1.5 million times. Beth Mole, Ars Technica, 28 Feb. 2022 Unfortunately, there’s a lot of contradicting and fallacious information floating around out there about how distance runners should and shouldn’t fuel to run fast. Outside Online, 12 Oct. 2020 Followers of QAnon also regularly show up at events and successfully spread new fallacious claims. New York Times, 20 Dec. 2021 Cannabis as a gateway drug seems to be a hypothesis based on simplistic and fallacious logical processes. Dario Sabaghi, Forbes, 7 Dec. 2021 But this is based on the fallacious notion that depletion of the resource means ever-higher prices. Michael Lynch, Forbes, 5 Nov. 2021 The thinking that dominates the institution is fundamentally fallacious. Steve Forbes, Forbes, 16 Sep. 2021 See More Word History
First Known Use
15th century, in the meaning defined at sense 1
fallacious
adjective
1
as in irrational
not using or following good reasoning it's fallacious to say that something must exist because science hasn't proven its nonexistence Synonyms & Similar Words
Relevance
- irrational
- unreasonable
- misleading
- unreasoning
- illegitimate
- illogical
- absurd
- unreasoned
- foolish
- weak
- silly
- invalid
- unsound
- inconsequent
- specious
- nonrational
- misguided
- sophistic
- inconsequential
- weird
- inconsistent
- meaningless
- sophistical
- asinine
- nonsensical
- preposterous
- eristic
- unusual
- odd
- strange
- unconsidered
- unconvincing
- insane
- random
- half-baked
- surreal
- senseless
- inexplicable
- ill-advised
- whacky
- rambling
- disorganized
- mad
- eristical
- reasonless
- disordered
- wacky
- unexplainable
- nutty
- peculiar
- unaccountable
- Kafkaesque
Antonyms & Near Antonyms
- logical
- reasonable
- valid
- rational
- sound
- wise
- sensible
- justified
- commonsense
- reasoned
- sane
- enlightened
- well-founded
- plausible
- persuasive
- sober
- informed
- convincing
- compelling
- just
- well-grounded
- true
- cogent
- clear
- credible
- solid
- certain
- organized
- satisfying
- demonstrated
- sure
- substantiated
- ordered
- confirmed
- established
- validated
- corroborated
2
as in misleading
tending or having power to deceive consumers who harbor the fallacious belief that credit-card spending will never catch up with them Synonyms & Similar Words
- misleading
- deceptive
- false
- incorrect
- specious
- delusory
- delusive
- ambiguous
- deceitful
- deceiving
- beguiling
- inaccurate
- fraudulent
- deluding
- dishonest
- mendacious
- subtle
- lying
- wrong
- perplexing
- cunning
- trick
- crooked
- bewildering
- puzzling
- confounding
- spurious
- dissembling
- untruthful
- underhanded
- wily
- untrustworthy
- bogus
- insidious
- tricky
- treacherous
- slick
- artful
- sneaky
- devious
- shifty
- forged
- guileful
- artificial
- counterfeit
- distracting
- sly
- crafty
- duplicitous
- shady
- perfidious
- trickish
- subtile
- hypocritical
- evasive
- faithless
- underhand
- fake
- knavish
- equivocal
- foxy
- feigned
- phony
- sneaking
- sham
- insincere
- defrauding
- jive
- ambidextrous
- circuitous
- backhanded
- fast
- phoney
- two-faced
- double-dealing
- left-handed
Antonyms & Near Antonyms
- straightforward
- forthright
- nondeceptive
- plain
- direct
- outspoken
- open
- frank
- candid
- illuminating
- explanatory
- straight
- aboveboard
- plainspoken
- openhearted
- clarifying
- revealing
- elucidative
- truthful
- revelatory
- free-spoken
- trustworthy
- foursquare
- honest