You know them when you see them. They are tapping on their smartphones, strolling into work late and amassing Instagram followers faster than a twerking cat. They complain. They “disrupt” stuff. They simultaneously (and somewhat improbably) like both Kanye West and Kenny Chesney.

They, according to the stereotype, are millennials, a group of 80-million-plus young adults born roughly between 1980 and 1996 whom researchers and marketers insist are bound by common values.

Jack MacKenzie, president of Magid Generational Strategies, a company in Los Angeles that analyzes generational trends for corporations, said that what millennials have in common is a lack of trust in authority, widespread tolerance, parental closeness, a desire to compromise and “a level of optimism that most people think is almost silly.”

And while some millennials are fine with defining (and defending) their generation, others, frankly, would like nothing to do with it.

In this respect their plight is not unlike that of Generation X, many members of which felt patronized by products like OK Soda, the movie “Reality Bites” and even “Generation X,” Douglas Coupland’s novel about twenty-something ennui in the late 1980s and ’90s. Today, “young people are far more heterogeneous than they were a few decades back,” Coupland wrote in an e-mail. “It seems pointless to lump them all into one creative slot.”

If millennials have cultural arbiters at all, they are, of course, online.

“We have these Twitter accounts, some of us command these huge audiences and we can essentially be saying whatever we want at our own behest,” said Leandra Medine, 25, creator of the fashion blog Man Repeller.

And some are using the Internet to try to redefine what their generation stands for, like David Arabov and Jonathon Francis, two founders of Elite Daily, a two-year-old news and entertainment website that bills itself as by and for Generation Y. Their motto, printed on black rubber wristbands given to every employee, is “aspire, believe, succeed.”

Overwhelming self-confidence and joie de vivre are the kinds of things that rub older millennials the wrong way. It inspired “Millennials in the Workplace,” a corporate training video parody, viewed more than 600,000 times on YouTube, that tells baby boomer bosses how to deal with twenty-something subordinates.

“I feel like their work ethic is a legitimate concern, even though it sounds like you’re a whiny old person complaining about the youth,” said Jared Neumark, 31, who produced the video for Official Comedy. “There’s this focus on enjoying your work, and that creates a huge problem because there needs to be a part of the population that has not-so-much-fun jobs, more labor-intensive jobs, or that are, like, lawyers.”

Studies by Paul Harvey, an associate professor of management at the University of New Hampshire, have also found that millennials have “unrealistic expectations and a strong resistance toward accepting negative feedback” at work. Harvey’s research into their workplace entitlement (spoiler alert: It’s high) was cited in a much-shared online piece “Why Generation Y Yuppies Are Unhappy.”

Older millennials look at teens and twenty-somethings and see a tribe that would die without the blue glow of smartphones.

“Their social interactions have always been woven into being digitally connected to people,” said Matthew Van Lewen, 30, of New York. “We didn’t grow up with unlimited texting plans, chatting all day long with our friends.”

They do agree on how much they loathe the name of their generation.

Tavi Gevinson, 17, the founder of the fashion magazine Rookie, said using the word makes her “feel like a traitor.”

“It’s like an adult term for teenagers,” she said. “I feel condescending if I use it around people my age and like I’m trying too hard, like a kid who swears a lot around older people, if I use it around adults.”