"The reason it's resonating so well with Gen Z kids right now is that it's such a simple, short response, and it's not aggressive," explains 18-year-old Nina Kasman, who sells "OK boomer" goods on Redbubble.com.

"It's passive. It means I'm not going to give you a full response because we know boomers haven't been listening to full explanations anyway," the student tells AFP.

"OK boomer" has become the retort of choice for Gen Z kids exasperated with the views of their elders -- and a potent pushback at those who dismiss today's youth as easily offended "snowflakes".

It is fueling countless memes on video app TikTok, emblazoning hoodies and t-shirts, and was even used by a member of New Zealand's parliament this week, forcing the older establishment to take notice.

"Boomer" is shorthand for baby boomers, a term used to describe people born during the uptick in birthrates that followed World War II. It generally means anyone born between 1946 and the mid-1960s when the United States enjoyed considerable prosperity.

But "OK boomer" refers to "a certain mindset," not specifically the age group, says Kasman, who attends Northern Illinois University. 

"People who are older who are fighting for the environment -- those people are not necessarily boomers in this context," she adds.

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Climate protests

The pithy phrase took off early this year as a comeback to older social media users, mostly white males, who attack the "safe spaces" and "trigger warnings" promoted by many young people in the name of inclusiveness and respect.

"We're just kind of tired of being put down for the things that the younger generation enjoys or believes in," says 19-year-old Everett Solares, who blames boomers for some of the ills affecting her generation.

"We're trying our best to bounce back from it," adds the University of Alabama student.

Generation Z roughly refers to those born after 1997. Millennials, also known as Generation Y, describes the group that came before -- those roughly born between 1981 and 1996.

Both groups are regularly said to be paying the price for the excesses of their parents' and grandparents' generations,  when education was cheap, car ownership soared, and it was easier to find a job and buy a house.

"It was possible to put yourself through college on a minimum wage job when the boomers were going to college, but that's incredibly impossible now," says Kasman. "We're pretty upset about it."

Generation Z -- to which climate activist Greta Thunberg belongs -- has been driving massive environmental protests around the world calling on adults to act to save the planet for future generations.

Thunberg regularly accuses older people of choosing to ignore scientists who largely agree that manmade warming is leading to a climate emergency.

Twenty-five-year-old New Zealand MP Chloe Swarbrick used "OK boomer" this week when she hit back at another politician who heckled her during a speech about climate change.

The catchphrase gained mainstream traction last month when it was featured in The New York Times -- and has triggered plenty of heated online debate with some older people retaliating.

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Death knell?

Star Trek actor William Shatner, who at 88 is not a boomer, called the jibe a "childish insult" after a Twitter user directed it at him.

American radio host Bob Lonsberry was heavily criticized after he compared "boomer" to a racial slur. The 60-year-old said it was "the n-word of ageism" in a since-deleted tweet.

"It's natural for generations to have conflicts as they vacate positions of power and move into positions of power," Cornell University sociologist and baby boomer Thomas Hirschl tells AFP.

"But we have more serious issues of contestation in our society today: increasing economic inequality and climate change -- these two things are existential threats," he adds.

In the meantime, both Solares and Kasman are keen to cash in, selling "OK boomer" merchandise on online marketplace Redbubble that ranges from t-shirts and hoodies to water bottles, stickers and socks.

Solares has made around $50 since launching her products two weeks ago but hopes to make more to help pay her student loan. 

For Kasman, it's more about being part of a movement and "taking back power" for her generation.

But will the phrase hang around for long?

"Very often when major media organizations get a hold of some new bit of youth slang, that marks the term's death knell!" linguist and lexicographer Ben Zimmer tells AFP.