leathcheann Posted in L Best definition leathcheann Leathcheann is Irish for you idiot. Best if used in school so that you can lie about what it means. TÃÂ¡ tÃÂº ar leathcheann dur. How satisfied are you with the definition? Looking for leathcheann meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 20 times.