ˈfaləsē, -si noun
( -es )
Etymology: Latin fallacia, from fallac-, fallax deceitful (from fallere to deceive) + -ia -y — more at fail
1.
a. obsolete : guile , trickery
b. : deceptive or false appearance : something that misleads the eye or the mind : deception
it appears that … the descent is perpendicular but this … is a fallacy of the eye caused by the distance — Anthony Trollope
2.
a. : a false or erroneous idea
parents console themselves by the American fallacy that one can only be young once — Elizabeth Bowen
b. : erroneous or fallacious character : erroneousness
the fallacy of such a suit for military use should at once be apparent — H.G.Armstrong
3. : a plausible reasoning that fails to satisfy the conditions of valid argument or correct inference — see formal fallacy , material fallacy , verbal fallacy