While "OTP" describes one's ultimate favourite pairing. "NOtp" describes one's least favourite pairing.
A fairly popular term in the shipping community.
Unlike, OTP - which is an acronym for "one true pairing", NOtp, simply plays with the fact that "O" sounds like "No". The "N" does not stand for anything.
Tumblr user 2: no dude gross they are totally my fuckin notp