Last August, the folks at Oxford Dictionaries published a list of words that they were adding to their dictionaries. Among them was neckbeard, which is listed as "A growth of hair on a man's neck." But this self-describing definition is not why the term was added. More interestingly, the term connotes someone with "poor grooming habits" and who's "socially inept."
To quote another source:
I used neckbeard as slang for (usually overweight) men who sit in their basement and play video games. Less about how bad they look (though they look bad) than who has them.
The word got my attention for two reasons. One was that neckbeards are men who are stereotypically associated with computers, whether as gamers or as programmers—which is to say, it describes people I've known.
The second reason was more purely linguistic: the term neckbeard uses a style of grooming as shorthand (or synecdoche) to tell us something about the person. This got me to wondering whether there are other metaphoric meanings based on tonsorial characteristics. And indeed there are.
For starters, the term neckbeard has itself spawned the word legbeard, a term for a woman who declines to shave her legs. Per Urban Dictionary, the connotations of the term are the same as neckbeard.
Moving back to the face, an obvious word based on hair characteristics is a graybeard, which is a term for an old man. (This is another term that I happen to have personal experience with.) There's also just plain beard in the sense of a disguise—a person who acts as a front for someone else. A beard might be a person who performs financial transactions in order to hide the real principal behind the money. A very specific meaning of beard in this sense is also someone who's a decoy in a relationship—for example, when a gay man dates (or even marries) a woman in order to conceal his sexual orientation. Over the years, Hollywood has abounded with rumors about actors and their supposed beards.
Moving upward on the head, something or someone who's highbrow is cultured. In contrast, lowbrow suggests lack of sophistication or breeding. The negative connotation of a small distance between the eyes and the hairline (that is, of a low brow) goes back at least to the 1700s. The metaphoric senses of a low or high brow were well established in the 1800s, and the 20th century added middlebrow, which splits the difference in terms of taste and sophistication.
One characteristic that's used to represent a person is lack of hair. For example, intelligence—or at least intellectualism—is sometimes associated with baldness. An egghead—the "egg" part here providing a lovely picture of hairlessness—is one term for an intellectual. Another term for an intellectual that I ran across recently is double-dome. In what sounds like a speculative etymology, Wiktionary suggests that "The word conjures the image of two bald-headed men putting their heads together in an effort to solve a problem."
Somewhat contradictorily, a longhair can also be a term for an intellectual, and especially for someone who likes classical music. This is a term whose meaning has been amplified in my own lifetime. When I was young, older people used longhair as noted here, to refer to intellectuals or classical-music fans. But I grew up in the 1960s, when hair fashion was changing, and longhair also came to be used for counter-culturalists who grew their hair out: that is, for hippies. Consider these two cites from the OED:
"He planned to become a 'long hair' musician... He wanted to be a composer of symphonies." (1967)
"Would hippies and long~hairs sit on the youth commission?" (1969)
You can see why this might have been confusing for a young person. But the two senses are united in that they refer to people whose hair style is a symbol of interests outside the mainstream.
Speaking of grooming, a greaser is not just someone who puts grease in his hair, but "a swaggering young tough, especially a member of a street gang." This sense of the word gave us the nostalgic musical Grease, but the word also has a considerably more offensive sense that's used as an ethnic insult. There are also skinheads, who shave their hair as a sign of belonging to a subculture primarily associated with racism.
And then there's color. Gray-haired, white-haired, and grizzled all refer to hair color, and by implication, age. (You might think, as I did, that the term éminence grise—an authority on a subject—likewise derives from hair color, since gris(e) is the French word for "gray." But the "gray" here refers either to the color of the habit worn by Pere Joseph, the original éminence gris, or to the shadowy dealings in which the monk tended to engage.)
Hair color, of course, need not be natural. A blue-hair is an older woman, so named because of the hair tint that such ladies sometimes use to remove a yellow cast to their gray hair. And a bottle blond is someone who's achieved a light shade only with chemical assistance.
What's notable to me about all of these terms is that they all have a negative cast. Calling someone a neckbeard or an egghead or a longhair or a bottle blond—well, these are not intended to be flattering descriptions. A possible exception is highbrow, but I'm not convinced that that word is always used in an admiring way.
But perhaps I've just been reading the wrong material. What other terms for hair styles (or lack-of-hair styles) are used as stand-ins for people?