The generations are engaged again, if not in warfare, then in the quiet, finger-pointy grumblings that are less about a search for meaning than a search for MEEEEaning.

It began when a millennial in New York Magazine chronicled the utter junkitude of coming of age in 2011; a Generation X writer for Gizmodo responded by telling the millennials to shut up already; a Slate cusper who was born in between Gen X and the millennials then entered the fray to announce that she didn’t feel like part of the fray. With the help of Twitter, she said, she had decided to christen her mini-cohort Generation Catalano, after a character on “My So-Called Life,” a 1990s television show that was canceled after one season. (We would have gone for Generation Jessie Spano, but . . . )

The 99 percenters, who are an all-ages group but tilt young, have occupied the Web with their student loan woes (and whoas — hello, $100K debt), and many of the boomers, the original My Generation, are alarmed and intrigued by the brashness of it all. When they hated their jobs, they whined to their spouses or consciousness-raised among friends. They did not tweet their revolution.

A long time ago, “generation” referred to fathers and sons and grandfathers — the familial process of getting older and spawning heirs — or to the literal waves of people who were being born and dying at roughly the same time. It was a convenient term, not an emotionally weighted one. Now the word “generation” has become a metaphor, a shorthand into which we pour our identities and dreams.

Each generation wants to assert its uniqueness, but would prefer to do it under an umbrella term: Witness the careful and studious attempts to decide just what came after Winona Ryder and Ethan Hawke. Millennials? Gen Y? Gen Why? “Digital natives” made it sound like the teens were going to meet up with Pilgrims, bearing cornucopias of cranberries and text messages.

(In the middle of all of this, shocking news: the University of Michigan’s Longitudinal Study of American Youth released an updated study revealing that the hallmarks that have frequently pockmarked Gen X — slacker, single, solitary — don’t really apply to the generation after all. They do not bowl alone. Reality does not bite.)

Who are we? What are we? Give us identities! Label us, please!

“It’s like Myers-Briggs or the DISC personality test,” says Anne Loehr. When people learn what generation they belong to, “then the light bulb starts to go off — ‘Oh, that explains why that is.’­­ ” Loehr is a generational guru, one of the people whose job now revolves around helping generations understand themselves and others. “When I started, people were like, ‘You do what?’. . . but now it’s much more the way our economy is working.”

This type of thinking began, as much as it could begin, with the French Revolution. The era was instrinsically tied up with the concept that society could make progress with the birth of each new, fresh generation. In 1812, the German writer Johann Wolfgang von Goethe (1749-1832) postulated that “anybody born only a decade earlier or later might have become a completely different person,” or, as the modern historian Robert Wohl later put it, “historical generations are not born; they are made.”

Generations became the ultimate nurture-over-nature data point — and not just parental nurture, but global. The evidence of collective behaviors and movements (beatniks, impressionists, baroque musicians) seemed to reflect evidence that cohorts were shaped by current events.

“Think about the sudden change in mood on Pearl Harbor Sunday, depending on whether or not you were old enough to enlist,” says Neil Howe, who, along with William Strauss, wrote the seminal “Generations,” coined the term “millennials” and is considered the foremost expert in the history of generations. When people fret, for example, over whether they are boomers or Xers, he asks them whether they can remember the assassination of John F. Kennedy. It’s the sort of go-to gestalt that can help shape a person’s whole way of being. It's been going on for centuries, he says.

“You can’t truly understand the Constitutional Convention in the 1780s unless you remember how the generation of Ben Franklin was so different from George Washington and Patrick Henry, which was different still than Madison and Monroe.”

Still, it seems safe to assume that previous generations didn’t care as passionately about their labels — most of which were retroactively developed by present-day researchers — as we do. We’re all familiar with the current crop of silents, greatests, boomers et al., but did people born in the 1530s ever bellow to people of the 1510s, “You’ll never understand me! You are Generation Catherine of Aragon, whilst I am Gen Boleyn?” Was it even possible to care this much about generational differences when the average life span was 42 years?

Now some generational theorists wonder whether the traditional concept of generations — set at about 20 years per wave — might actually be changing, due to the quick turnover of technology. Generation MySpace is different from Generation Facebook, and Generation E-mail is different from Generation Text.

Hundreds of generations, crammed into one life span.