According to a One Direction fandom site, the slang abbreviation ot5 stands for "one true," referring to the five original members of 1D: Zayn, Niall, Louis, Harry, and Liam.

If you're a fan of the boys guys, you've probably seen the term used on social media. The hashtag #ot5 is circulating around Twitter among the fanbase with the recent reunion tease.

"Honestly If it’s not #ot5 idk if I want it....." one fan tweeted, seemingly referencing the idea that Zayn should be part of the 10-year reunion. Another individual wrote, "So I’m just going to spend the rest of the week refreshing Twit and Insta for 1D reunion content?  Oh, okay. This is apparently who I am now. Cool, cool.  I’ve embraced it. Let’s gooooo.  #10YearsOneDirection #1DReunion #OT5."

One fan tweeted, "When your watching a playlist of one direction videos and then zayn stops being in them #10YearsOneDirection #ot5." This fan posted, "I KNEW MY BOYS WOULD COME BACK!!! #onedirection10years #ot5." 

So, are the guys officially reuniting?