noun. A scene or brief moment in a motion picture, featuring some element of sophomoric or childish humor, that is out of place, and inapropriate to the advancement of the story. It seems to exist for no other reason than to make an idiot laugh for about 2 seconds.
Named in honor of George Lucas, for his propensity for including these inane moments in his films.
Lucasisms of note include:
An alien stepping in poop outside of Mos Eisley in Starwars I
A wookie giving a tarzan yell as he swings from a vine in StarWars III
Wow, that was stupid. I can't believe this director would put a Lucasism in his movie.