adjective

1. Seemingly well-reasoned, plausible or true, but actually fallacious.

   “This idea that we must see through what we have started is specious, however good it may sound.”

2. Employing fallacious but deceptively plausible arguments; deceitful.

3. Having an attractive appearance intended to generate a favorable response; deceptively attractive.

Synonyms: fallacious, insincere, meretricious, pretextual