Do you know what a gyat is? What about a rizzler? And how, precisely, does one pay a Fanum tax?

Welcome to the language of Gen Alpha, the cohort coming up right behind Gen Z. These children of Millennials have begun a generational rite of passage — employing their own slang terms and memes, and befuddling their elders in the process.

Which brings us back to gyat (rhymes with “yacht,” with a hard “g” and a firm emphasis on “yat”).

“There’s no cute way to say it — it’s just a word for a big butt,” said Alta, a 13-year-old eighth grader in Pennsylvania. “If someone has a big butt, someone will say ‘gyat’ to it.”

Alta and her brother Kai, an 11-year-old sixth grader, said they had learned the word on TikTok and that it had suddenly become popular among their classmates. The internet encyclopedia Know Your Meme credits the sudden popularity of “gyat” to the Twitch livestreamer Kai Cenat. (In August, Mr. Cenat made headlines when his fans swarmed Union Square Park in Manhattan after he promised to give away gaming consoles at no cost.)

“I don’t say ‘gyat’ to people, though, unless they’re my friend,” Alta said. “And we say it to our mom.”

Several other new words have become part of this generation’s vernacular, and six members of Gen Alpha offered their decoding services for this article. (Their parents gave permission for them to be interviewed, with the agreement that their last names would not be used.) Many of the children cited a catchy parody song making the rounds on TikTok as a key to the slang’s rising popularity. The lyrics go like this:

Sticking out your gyat for the rizzler

You’re so skibidi

You’re so Fanum tax

I just wanna be your sigma

A rizzler is a “good person,” according to Malcolm, a 10-year-old in Washington state.

“Having rizz is when you have good game,” Alta said. “Being a rizzler is like when you’re a pro at flirting with people.” (Rizz is short for charisma.)

The word can be used as a compliment or a joke, according to Jaden, 12. She said that the boys at her school in New Jersey had been singing the song lately, adding that it gave her a headache.

Jaden added that “nobody really knows” the meaning of “skibidi.” It has entered the lexicon by way of the animated series “Skibidi Toilet,” which has racked up more than 700 million views on YouTube. A typical episode is about 15 seconds long and features a man who pops his head out of a toilet bowl and launches into a song heavy on the use of the word that gives the show its name. (It’s easier if you just watch it. Boomers might think of “Skibidi Toilet” as a 2020s answer to the animations of “Monty Python’s Flying Circus.”)

“I don’t like,” Tariq, 8, said of the series. “It creeps me out. Every time I go to the toilet, I just want to get it quick done.” Tariq, who lives in New York State and is known online as Corn Kid, said he was not familiar with the other terms.

Fanum tax refers to Fanum, a popular streamer on Twitch who regularly appears online with Mr. Cenat. When friends are eating in Fanum’s presence, he insists that they share some of their food with him. That’s the Fanum tax.

And sigma has something to do with wolves.

“Everyone in my grade, at least, says it in a way where they’re like the alpha of the pack,” Alta said. “If you’re trying to say you’re dominant and you’re the leader, you’ll call yourself ‘sigma.’”

In a TikTok video posted in October, Philip Lindsay, a special-education math teacher in Payson, Ariz., listed a few terms he had been hearing in the classroom, including Fanum tax and gyat. “Which does not mean ‘get your act together,’” Mr. Lindsay, 29, said in the video, which has since been viewed over four million times.

His students tried at first to make him believe that gyat was an acronym that stood for “go you athletic team,” he said in an interview. He recently had to explain gyat’s real meaning to a colleague whose students had convinced the teacher to display the word in the classroom.

Mr. Lindsay said the new words struck him as more “meme-like” than earlier slang terms. He added that he believed they were “driven mainly by social media, TikTok specifically.”

Gen Alpha is still being born, according to demographers. Its birth years span from 2010 to 2025, said Mark McCrindle, a generational researcher in Australia who coined the name Gen Alpha several years ago.

Online, members of Gen Z have begun to realize they are no longer the new kids on the digital block — and that Gen Alpha might be coming for them, in the same way that they had once gone after millennials.

Anthony Mai, a TikTok creator with a large following, recently posted a video of himself wearing a comically deadpan expression as the Gen Alpha-slang song played. “Gen Alpha is making their own memes now,” he wrote in a caption. “It has begun. We are the next cringe gen on the chopping block.”

Intergenerational comedy has become a staple on social media platforms, where creators dramatize the differences between age groups. Skibidi and gyat fit snugly into the memes and video shorts belonging to this subgenre.

“Whenever I think about the linguistic differences between generations, I just think, Are we really going to do this again?” said Jessica Maddox, an assistant professor of digital media at the University of Alabama. “Generational differences and divides have always been played up to some extent, even before the heyday of the internet, but social media really exacerbates them.” She cited “OK, boomer,” a retort popularized online by Gen Z in 2019, as an example.

As Gen Alpha’s slang terms make their way into the wider (read: older) world, the young people responsible for their popularity are ready to move onto what’s next.

“If millennials start saying them, we’ll be like, ‘We’re done with these now,’” Jaden said.