WASHINGTON — The hashtag gave it away.

When a Florida jury convicted Michael Dunn of attempted murder, but not actual murder, in the shooting death of black teenager Jordan Davis, the hashtag #dangerousblackchildren popped up on Twitter. Users posted photos of black babies and toddlers, spoofing the fear that Dunn testified he felt before opening fire on a carful of teens at a convenience store.

That hashtag was the calling card of Black Twitter, a small corner of the social media giant where an unabashedly black spin on life gets served up in 140-character installments.

Black Twitter holds court on pretty much everything from President Barack Obama to the latest TV reality show antics. But Black Twitter can also turn activist quickly. When it does, things happen — like the cancellation of a book deal for a juror in the George Zimmerman trial, or the demise of Zimmerman’s subsequent attempt to star at celebrity boxing.

Catchy hashtags are a hallmark and give clues that the tweeting in question is a Black Twitter thing.

“It’s kind of like the black table in the lunchroom, sort of, where people with like interests and experiences, and ways of talking and communication, lump together and talk among themselves,” said Tracy Clayton, a blogger and editor at Buzzfeed known on Twitter as @brokeymcpoverty.

Black Twitter is not a special website or a smartphone app. The hashtag #blacktwitter itself won’t necessarily lead you to it. It doesn’t exactly stick out among the trending topics on Twitter, even though it’s been known to cause a topic or two to trend. It is not exclusively black — there are blacks who don’t participate in it, and people of other races who do.

“Black Twitter brings the fullness of black humanity into the social network and that is why it has become so fascinating,” said Kimberly C. Ellis, who has a doctorate in American and Africana Studies, tweets as @drgoddess and is studying Black Twitter for her upcoming book, “The Bombastic Brilliance of Black Twitter.”

According a Pew Research Center report, while similar numbers of blacks and whites use the Internet — 80 percent and 87 percent, respectively — 22 percent of those blacks who were online used Twitter in 2013, compared with 16 percent of online whites.

Meredith Clark, a doctoral candidate at the University of North Carolina at Chapel Hill who is writing her dissertation on Black Twitter, likened it to “Freedom’s Journal,” the first African-American newspaper in the United States. On that publication’s first front page in 1827, it declared: “We wish to plead our own cause. Too long have others spoken for us.”

“If you are from a particularly marginalized community or one where others have spoken for you, but you have not had the agency to really speak for yourself or make your truth known, then it is absolutely necessary that in any instance you can take on that agency that you do so,” said Clark, who tweets from @meredithclark. “And so that is what you see happening in Black Twitter.”

Mainstream U.S. media first took serious notice of Black Twitter last year, when it abruptly rose up to scuttle a book deal for a juror in the trial of Zimmerman, who was acquitted of murder in the death of Trayvon Martin. That was the first time that blacks used Twitter “in a very powerful and political way,” said Houston black social media consultant Crystal Washington.

Most recently, Black Twitter reared its head through hashtags like #stopthefight, to protest a proposed celebrity boxing match supposedly between Zimmerman and rapper DMX. The promoter quickly canceled after a flood of Twitter complaints.