MILWAUKEE (CBS 58) -- Generation Z has a new rallying cry. 

"OK, boomer" become popular on the video app Tik Tok. It has since exploded into a clapback against adults.

Critics have called it ageist. One attorney warns it's not okay to say in the workplace.

"What the speaker intends is not what's critical. It's how the recipient understands what's being said. And the phrase OK, boomer can be understood by the recipient as an ageist term."

There's an "OK, boomer" song, t-shirt, even a write-up in the New York Times. It's rubbing some people the wrong way, but one man says it's fair play.

"I think it's fair play. I think it's fair play," said Michael Drescher of Milwaukee. "I get it. I think sometimes boomers are just as guilty as everything we accuse them of."