There are a lot of words in the English language that are considered taboo, and being a family friendly site, I don't feel the need to cite examples here. However, I will say what I think the worst word a chessplayer can use is, so brace yourselves....
OK, it's out. As a serious chessplayer, the aforementioned word often feels like blasphemy to me, in spite of it being a totally normal word that is used every day in conversational and written English. However, the way one would use it in chess would be something like this:
"I **** missed that he could ignore my threats"
To me, **** is an attempt to simplify something that is not meant to be simplified. Chess is a beautifully complex game, full of deep calculation, understanding, and harmony. To try to take all of that complexity and whittle it down to a point where it can be described in a couple of words, and this horrible expletive **** implies that there is nothing else of note in the position. In my experience, it is NEVER the case that there is nothing else of note in a position other than **** followed by a few words. If you missed an idea or a resource your opponent had, you are doing yourself a huge disservice by thinking "I **** missed this move" as opposed to "I overlooked this resource my opponent had because (Insert one: I was low on time because of poor time management, I was too optimistic about my chances, I was not thinking prophylactically enough, I got tooexcited/impulsive, etc). Even if you'd refer to a position you got as "**** won" or "**** lost", if that really was all there is to it, the game would already be over because somebody would have resigned. The position might be objectively won, but you still have to demonstrate proper technique. If it's objectively lost, you still can try to make your opponent's life as difficult as possible. "****" can also be used to imply that you have a very simple plan, you want to achieve one thing and one thing only, typically something relatively unambitious. This is a very poisonous way of thinking; you should always try to extract the maximum from a position instead of contenting yourself with "****" making some small progress. This is not to say that you should never content yourself with making small steps toward a larger goal- this is very much a part of chess- but you should appreciate the complexities and only make small progress if it is the maximum you will attain. To conclude, I'll leave the readers with a position I reached in the last tournament I played, the Barcelona Open, which was very obviously objectively lost (starting after 8. ... Ne5??). Had my opponent played perfectly I surely would have lost the game- my position was even objectively lost for over 40 moves- but by looking for all the defensive resources in the position, I managed to apply enough pressure to make the win a little difficult, and one small error on his part led to another and I ultimately drew a game I seriously considered resigning on move 9.
Best Wishes to All, and never say the word "****" in reference to anything chess-related!
GM Sam Shankland