adj. 1. Pertaining to the TV show "The Simpsons". From the Simpsons and -ian, a common adjective suffix.
2. (often cap. S) A museum dedicated to Simpson paraphenalia. From Simpson and Smithsonian, the institution that runs many of the museums in Washington, D.C.
1. "No one has a greater amount of simpsonian knowledge than John; he watches the show everyday."
2. After visiting the Flintstones Museum, the family went to the Simpsonian, where they saw original storyboards.
by A_1_B_2_C_3_________________ September 30, 2006
Any one of the few people who still believe that The Simpson's is better than Family Guy.
Dude 1) Hey, did you see Family Guy last night?

Dude 2) Family Guy!?! That show sucks! The Simpson's are sooooooo much better!

Dude 2) Dude, you're such a Simpsonian
by UltimateShadow January 30, 2010
A bright yellow, spiky-roofed museum on the Mall in Washington, celebrating the Lisa Simpson Presidency. As pre-cognitively laid out in the March 19, 2000 episode, 'Bart to the Future', Lisa has been elected and has moved into the Oval Office to clean up the mess left by President Trump.
On her lunch break, Jane would wander over to the Simpsonian Institution, dreaming of a country under President Lisa, with clean air and water, kindness to all people and animals, the return of ethics and honesty to government, and Mr. Burns in prison.
by Monkey's Dad March 1, 2020