You are correct that the literal definition of cuckold is a man whose wife is unfaithful.From Merriam-Webster:
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Being cheated on literally makes you a cuckold. That’s the purest sense of the term.
If your partner has relations with someone else, regardless of you knowing about it, you are a cuckold.
We do have an archaic term, wittol, that’s used when you know and tolerate it, but that’s just lumped into the generalist term cuckold now.
Generally, the difference is how you respond to it.
Like it and even encourage/tolerate it? Netorase.
Dislike it and wish it to stop? Netorare.
Yes, like can turn to dislike and vice/versa. Therefore, I tend to use the majority rule to classify works.
If a significant number of scenes revolve around the MC enjoying the cheating, then it is NTS (netorase).
And if he is suffering throughout the scenes? NTR (netorare).
I do agree the lines between NTS/NTR often get blurred. In those cases, it can be useful to defer to the legendary words of Mr. Stewart: “I’ll know when I see it.”
However the word is used connotatively for a man who is both aware and accepts his wife's unfaithfulness.
In the west, Netorase would be Cuckoldry while Netorare would be Unwilling Cuckoldry.