under sextimate Posted in U Best definition under sextimate The act of under estimating one’s sexually ability. That girl’s fuglyness led me to assume she would be bad in bed. Oh but did I under sextimate her, that was the best night of my life. How satisfied are you with the definition? Looking for under sextimate meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 104 times.