Truel

This word is not in any dictionary that I have easy access to, and I'm not going to search every online dictionary for it. I have googled it, and it's obvious that if it is a word, it's a specialised word used in game theory; so the question should make this clear.

Wikipedia (you will not be surprised to hear) has a page for it, and it gives an alternative word – friel – which (even if only on the grounds that it's given on Wikipedia) should have been allowed as an alternative answer.