A Lexicon of the Internet, Updated by Its Users Jim Wilson/The New York Times The Urban Dictionary site, started in 1999 by Aaron Peckham, has become an archive for nearly any new term or slang word, particularly those related to social media and the Web. SAN FRANCISCO - Millions watched and gossiped online as Miley Cyrus "twerked" on stage at MTV's video music awards in late 2013. Then, they rushed to Urban Dictionary to figure out what that was - making "twerk" one of the most-searched terms on the site all year. That is just one of many examples of how Urban Dictionary, a crowdsourced online dictionary that lets anyone contribute words and definitions, has become the anthropologist of the Internet, taking the pulse of the web and capturing cultural moments in real time. The site was started in 1999 by Aaron Peckham, then a college freshman. Since then, it has become an archive for nearly any new term or slang word, particularly those used to describe the behavior and activities that have risen because of social media and the Web. More than seven million definitions of words, acronyms and phrases are listed on the site, and 2,000 definitions are added daily. The site's audience has grown steadily, as well. In October 2013, 8.4 million people checked the website monthly, up from six million in November 2010, according to comScore. Mr. Peckham says his own internal figures are higher. It has slowly crept into the collective and cultural consciousness as a default dictionary, with recent casual references by figures like Jon Stewart on "The Daily Show" and the morning hosts on "Good Morning America." It has even become a source for judges trying to figure out the latest slang. Despite its audience and reach, Urban Dictionary is not the locus of most online activity. Words, photos and videos flood Facebook, Instagram, Twitter and Snapchat, giving those sites their multibillion-dollar value - or perceived value - and hype. Urban Dictionary, instead, has become the archive of all the words and phrases of this still-forming culture of social media, like "selfie," "snapchat" and "status update." And that is precisely what makes Urban Dictionary's role important, said C. W. Anderson, a professor of media culture at the City University of New York. "The Internet is everywhere, but it has its own regional vernacular," he said. And those expressions move into standardized language. That process is occurring - like everything else - far more quickly. What's different now is that it's being transcribed and written down. Urban Dictionary, he said, "allows us to see that process in real time." "It's something that other social and online media sites haven't really done," he added. Although Urban Dictionary predates Instagram, Snapchat, Tumblr, Twitter and even Facebook by a few years, it does not garner the double-digit stock price and billion-dollar bids from eager buyers that are standard fare in Silicon Valley. It is a more modest business, run by Mr. Peckham, its 32-year-old founder, out of his home in San Francisco. When Mr. Peckham has a meeting in the city, he borrows an office from friends who work at Pivotal Labs, a development agency. But they have no affiliation or monetary involvement in his site or company, he said in an interview here at the company's sunny, glass-walled conference rooms. Mr. Peckham, affable and good-natured, prides himself on his independent status, saying he originally started the site because he did not like the idea that "a printed dictionary, which is updated rarely, tells you what thoughts are O.K. to have, what words are O.K. to say." The child of a public-school teacher and an artist, Mr. Peckham has a history of making satirical Internet sites. While he was studying computer science at the California Polytechnic State University in San Luis Obispo, he created a spoof of Ask Jeeves, the search engine. It wasn't long before he received a cease-and-desist order. After he shut that site down, he turned his attention to a site that satirized Dictionary.com. "At first, all the content was by me and my friends, having fun," he said. But after he graduated, he continued to tinker with the project, named Urban Dictionary, even though he had a job at Google. That job didn't last long though; after two years, he quit in 2008 to work on Urban Dictionary full time. "I just wanted to work on one project that represents me," he said. Mr. Peckham said he had not sought or accepted any venture financing for the site. The company makes money, he said, mostly from advertising and a small collection of Urban Dictionary-related products like calendars, greeting cards and books that he sells through the site. Mr. Peckham said his company did not generate a huge amount of cash - though he declined to give specific figures - but said it was enough to support him and the site. "It's stable and growing," he said.