Today's word is: cuspidor (from Season 1, episode 2).
After Bart lies on his aptitude test and is declared a genius, Marge gets tickets for the opera, hoping it will foster his intelligence.
Bored out of his mind, he changes the lyrics in the musical "Carmen" to: "Toreador, oh, don't spit on the floor. Please use the cuspidor, that's what it's for!"
Turns out a cuspidor is a spitoon, or a pot used for spitting. Gross, but when you think about it, it is a much better location for spitting than the floor, so thanks, Bart!