Hashtag (noun)

1. A symbol (#) used before a word or phrase to indicate that it represents a keyword or topic of interest on social media.
2. A word or phrase preceded by a hash sign (#), used to identify messages on a specific topic and make it more discoverable on social media platforms.

Origin:

Coined in 2007 by chris messina as a way to organize tweets on twitter, it is a combination of the pound sign (#) and a word or phrase without spaces.

Examples:

1. The hashtag #Oscars was trending on Twitter during the Academy Awards.
2. I've been using the hashtag #WorkFromHome to keep track of tweets about remote work.
3. By including the hashtag #BlackLivesMatter in their tweets, people showed their support for the movement.
4. Using the hashtag #ThrowbackThursday is a way to post an older photo on social media on Thursdays.
5. I"ll be live streaming on #Twitch at 8pm tonight, don"t forget to tune in!