definition of nemeses
nemÂ·eÂ·sis. n. pl. nemÂ·eÂ·ses (-sÄzâ²). 1. A source of harm or ruin: Uncritical trust is my nemesis. 2. Retributive justice in its execution or outcome: To follow the proposed course of action is to invite nemesis. 3. An opponent that cannot be beaten or overcome. 4. One that inflicts retribution or vengeance. 5.