A tuckerization is the intentional use of a real person’s name in a fictional story without necessarily basing the fictional character’s personality or appearance on that real-life individual.
Generally the person being tuckerized is not a public figure. For instance, portraying George W. Bush as the President of the Confederate States of America in your alternate-history novel would not be a tuckerization. Accidentally naming a minor character Belinda Smith when your second cousin is also named Belinda Smith may look like a tuckerization (and may require some explanation at the next family reunion) but it isn’t; genuine tuckerizations require intent.
Naming a heroic doctor in your urban fantasy novel after the bartender at your neighborhood watering hole is definitely a tuckerization. So is naming an AI program after your college sweetheart.
Tuckerizations are sometimes in-jokes, sometimes tributes to beloved friends, and sometimes offered as auction/raffle prizes in the name of charity or in the name of the author avoiding foreclosure for another month. They’re a very common type of backer award in crowdfunding campaigns.
The term comes from science fiction author Wilson Tucker, who often named minor characters in his stories after his friends.
It’s usually fine to name that doomed redshirt in Chapter 2 after a buddy. But in general, it’s best not to name despicable characters after real people unless you have their permission. If the character is even slightly like the real person, and if the target of your tuckerization lacks a sense of humor about the whole thing, you are potentially opening yourself up to a libel lawsuit or other unpleasantness.