The name for the hash sign (#) added to a word or phrase that lets Twitter users search for tweets similarly tagged.

Historical perspective: On September 1, 2007 the hashtag—formerly known as the lowly pound sign among other names—was first used on Twitter, by Chris Messina, then a Google product designer. Messina, who had attended the South by Southwest conference  was looking for ways to make it easy for attendees to find each other, so he tweeted out “how do you feel about using # (pound) for groups. As in #barcamp?” By a decade later, the hashtag evolved into part of our pop culture as some 125 million hashtags are shared every day on Twitter, and the sign has been adopted by tens of millions of users on other social networking sites like Facebook, Tumblr, Slack, and Instagram. It’s even infiltrated our vernacular, punctuating jokes and everyday chats.

In 2017, according to NYMag.com, the most popular hashtag was #BTSBBMAS, which aimed to get the Korean-pop band BTS a trophy at the Billboard Music Awards, with more than 300 million tweets. In fact, of the most-used hashtags over the past 10 years, five of them—#MTVHottest, #MTVStars, #KCA, #iHeartAwards, #FanArmy—involved fans tweeting about awards shows. #BlackLivesMatter might get the headlines, but it’s groups like Justin Bieber’s #Beliebers who keep the hashtag movement alive. “#TheMoreYouKnow.”

See also : dag-tag  hashtag activism  #word  TFA  
NetLingo Classification: Online Jargon