A person who claims to be a black belt in
karate, but who actually only studied for a couple of months or not at all.
ETYMOLOGY - This word comes from the name of a fictional character named Daniel Larusso, who was the protagonist in "The Karate Kid"; a mediocre but hugely successful
American film released in the early 80's which starred Pat Morita and Ralph Macchio.
After he got his ass kicked by that green belt, I figured he had to be a Larusso.