So, there was a discussion in the other threa.
I did not expect me learning what NTR means becoming useful that soon, but here we are:
(Context: main character cheated on his wife out of spite, but she just shrugged it off when she found out and he is not happy about that outcome; also, did he hope to get killed, wtf?)
Usage seems to confirm what @Biblio said about it just meaning “cheating”.
Edit: also, the only other choice he can think about is “crying oneself to sleep”. I find it weird that “talking about it” isn’t even one of the options that come to his mind…