[3] In the episode, Homer accidentally saves the Springfield Nuclear Power Plant from meltdown by arbitrarily choosing the emergency override button using a counting rhyme.

Homer is honored as a hero and idolized by his daughter Lisa, but feels unworthy of the praise, knowing his apparent heroism was blind luck.

Meanwhile, Bart is downhearted after learning that Milhouse's mother forbids the boys to play together anymore because she thinks he is a bad influence on her son.

Basketball player Magic Johnson of the Los Angeles Lakers made a guest appearance in the episode as himself, becoming the first professional athlete to do so on the show.

In its original airing on Fox, "Homer Defined" acquired a 12.7 Nielsen rating—the equivalent of being watched in approximately 11.69 million homes—and finished the week ranked 36th.

Unable to remember his safety training (because he was playing with a Rubik's cube at the time), Homer chooses a button at random with a counting rhyme, which miraculously averts the meltdown.

Burns introduces Homer to Aristotle Amadopolis (Jon Lovitz), the owner of the nuclear power plant in the fictional neighboring city of Shelbyville.

The recording of the episode was done during the National Basketball Association's regular season, so the producers had a hard time scheduling Johnson's session.

[4] Director Mark Kirkland wanted the Springfield Power Plant to "look the best it had to date" and inserted shadows and back-lighting effects to make the panels in Homer's control room glow.

The authors of the book I Can't Believe It's a Bigger and Better Updated Unofficial Simpsons Guide, Warren Martyn and Adrian Wood, described it as an excellent episode which added new depth to the show in the scene with Marge trying to convince Luann to let Milhouse play with Bart again.

They added that Lisa's "faith in her heroic father makes a nice change", and said that the episode's ending, in which Homer enters the dictionary, "is most satisfying".

[20] Nate Meyers of Digitally Obsessed rated the episode a 4 (of 5), writing that he enjoyed the Homer story but found the Bart and Milhouse subplot more interesting.

[21] The San Diego Union's Fritz Quindt said the animators "did [Johnson's] likeness good," and noted that in the game the "colors on the Lakers jerseys and the Forum court were correct.

"[23] Johnson's appearance was broadcast on CNN's Sports Tonight the day before the episode originally aired, and host Fred Hickman said he did not find it humorous.

[24] Lisa sees this title and criticizes the newspaper as a "flimsy hodge-podge of high-brass factoids and Larry King", to which Homer responds that it is "the only paper in America that's not afraid to tell the truth: that everything is just fine".

[24][25] In the book, Gray says this scene is used by the show's producers to criticize "how often the news is wholly toothless, sacrificing journalism for sales, and leaving us not with important public information, but with America's Favorite Pencil".