Stands for 'One True Pairing', for instance a couple that would or is perfect for each other.

One true pairing. A term you use to express a pair of people that are the perfect partner for each other. Gender doesn't matter.

One true pairing. Usually involving some kind of fandom.

Stands for One True Pairing, used by fandoms (such as fanfictions, fanarts, fanvids, etc.) to describe two characters that are meant to be together.

When you have two characters in a show you like to pair together, and you want them to be your children but also be your parents but also you want to see them fuck but then you’re usually attracted to one or both of the people involved so ultimately what the fuck kind of complex is that

One Tasty Poptart

The term OTP has many meanings, such as On The Piss (Drinking terms), Outside The Perimeter (Atlanta slang), One True Pairing (In Fandoms), and many other meanings.