1. containing or based on a fallacy - fallacious reasoning - an unsound argument • Syn: unsound • Similar to: invalid • Derivationally related forms: unsoundness (for: unsound), fallacy, fallaciousness 2. intended to deceive - deceitful advertising - fallacious testimony - "smooth, shining, and deceitful as thin ice" - S.T.Coleridge - a fraudulent scheme to escape paying taxes • Syn: deceitful, fraudulent • Similar to: dishonest, dishonorable • Derivationally related forms: fraudulence (for: fraudulent), deceitfulness (for: deceitful) 3. based on an incorrect or misleading notion or information - fallacious hope • Similar to: incorrect, wrong • Derivationally related forms: fallaciousness
