Another term for the pound symbol or hash sign (#).
Etymology: coined in the 1960s by researchers at Bell Labs.
Watchers of @Midnight know that the show has a recurring bit called "hashtag wars".
Last week they did a retro 80s episode - complete with dial-up sounds - and replaced "hashtag wars" with "pound sign wars", a.k.a. "octothorpe wars".
(Rather than texting your contributions to the night's theme, you could fax them.)
For us old-timers, it was an amusing episode.