specious

adjective4

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.

   • With early virtues plant your breast, / The specious arts of vice detest. — 1727
3. •
   Having an attractive appearance intended to generate a favorable response; deceptively attractive.

   • And could any thing be more specious, or more equal, than that fair distribution of power and profit, which men called the NEW MODEL? — 1760
4. •
   (no longer used) Beautiful, pleasing to look at.