[fal.la.cy] n, pl -cies [L fallacia, fr. fallac-, fallax deceitful, fr. fallere to deceive] (14c) 1 a obs: guile, trickery b: deceptive appearance: deception
2. a: a false or mistaken idea "popular fallacies" b: erroneous character: erroneousness
3: an often plausible argument using false or invalid inference