I think this has the potential to become one of THOSE topics.
IMO a blunder is a move which, with best play on both sides, changes the outcome of the game in your opponents favour.
So, if you are winning, and you make a move which allows your opponent to draw or win, that's a blunder.
If your opponent now does not take advantage of this and gives the win right back to you, that's also a blunder.
If you are rated under 2000, probably about 1 in 5 moves is a blunder.
Hello everyone, i'm kinda confused of what "blunder" means. If you make a mistake it's called a blunder, right? But if your opponent doesn't notice did you make a blunder? Do both of us make a blunder? or nobody makes a blunder?