certaintyn.[OF. certainet.]1. The quality, state, or condition, of being certain.()The certainty of punishment is the truest security against crimes. (Fisher Ames.)2. A fact or truth unquestionable established.()Certainties are uninteresting and sating. (Landor.)3. (Law) Clearness; freedom from ambiguity; lucidity.()Of a certainty, certainly.()