OT3

plural OT3s

1. slanglifestyleOne true threesome; a polyamorous ship involving three characters that is a personal favorite of a fan.

   And you don't have to limit your favorite ship to two characters — if there's a third involved, they can be your OT3.

   2015, Sam Maggs, The Fangirl's Guide to the Universe: A Handbook for Girl Geeks, page 31

   2 more examples

   For some, each member of the triangle cares deeply for the other two, like Elena/Damon/Stefan and Scott/Allison/Isaac—both the most popular OT3s in their respective fandoms.

   2017, Charity A. Fowler, "Negotiating Desire: Resisting, Reimagining and Reinscribing Normalized Sexuality and Gender in Fan Fiction", dissertation submitted to Virginia Commonwealth University, page 286

   Not only are male characters often presented as unapologetically bisexual (or, in some sense, post-sexual), but OT3 partnerships are not uncommon.

   2018, Lucy Neville, Girls Who Like Boys Who Like Boys: Women and Gay Male Pornography and Erotica, page 237