/fal"euh see/ , n. , pl. fallacies .
1. a deceptive, misleading, or false notion, belief, etc.: That the world is flat was at one time a popular fallacy.
2. a misleading or unsound argument.
3. deceptive, misleading, or false nature; erroneousness.
4. Logic. any of various types of erroneous reasoning that render arguments logically unsound.
5. Obs. deception.
[ 1350-1400; fallacia a trick, deceit, equiv. to fallac- (s. of fallax ) deceitful, fallacious + -ia -Y 3 ; r. ME fallace ]
Syn. 1. misconception, delusion, misapprehension.