Ｉｓ ｉｔ ＮＴＲ ｉｆ ｔｈｅ ｇｉｒｌ ｇｉｖｅｓ ｈｅｒ ｃｏｎｓｅｎｔ， ｂｕｔ ｓｔｉｌｌ ｄｏｅｓｎ’ｔ ｌｉｋｅ ｉｔ？
NTR is, to my knowledge: when one person assumes the role of another in a relationship.
Thus it is not NTR when a wife/husband has sex with a stranger. It IS NTR when they decide they will mostly/only have sex with that stranger from now on.
If a character is cheating against their volition, and against their desires, it can still be NTR, as long as the role of "lover" is assumed by the rapist. For example, if a robber breaks into a house and ties up the husband while repeatedly raping the wife, to the point where the husband pretends it is part of their normal life, then it is NTR.
>In evolutionary biology, the term cuckold is also applied to males who are unwittingly investing parental effort in offspring that are not genetically their own.
Fuck off moot