What does "paradox" mean?

Paradox: A tenet or proposition contrary to received opinion; an assertion or sentiment seemingly contradictory, or opposed to common sense; that which in appearance or terms is absurd, but yet may be true in fact. A gloss there is to color that paradox, and make it appear in show not to be altogether unreasonable. Hooker. This was sometime a paradox, but now the time gives it proof. Shak. Hydrostatic paradox. See under Hydrostatic.