What is the definition of a blunder?

I've found bizarre blunder flags in the chess.com computer on several occasions. For example missing a mate in 4 in favour of a mate in 5... Surely that should not be classified a blunder!

I think a blunder should be a move that alters the course of the game. E.g. A move that turns a win into a draw or a draw into a loss. The single pawn definition. Maybe is appropriate for masters but not for me and the people I play against!!

I don't think that dropping a pawn is a blunder, unless it's the endgame.

It's only simple if you ignore the rest of the thread...which indeed you've managed to do rather well.

Yes, that's the standard dictionary definition.  But dictionaries aren't generally too chess-specific...

Ah yes, suggesting a rather well-worn path for this thread to follow (speaking of blunders).

These aren't offical definitions, but from what I can tell studying my game analysis, they are pretty good descriptions.

I would consider an "inaccuracy" a move that doesn't really make the most of your position, but doesn't forfeit your advantage either. A good example would be when you play an alternative correct move in Chess Mentor. It still will win, but is slower, thus resulting in your opponent being able to close the gap more than, if you would have been more proactive or straightforward. Typically this is when you play a move in a positional manner, instead of in a tactical manner, though stonewalling and marching are ultimately just as effective in the win column, as forcing an exchange or two.

A mistake is a move that will either cause you to forfeit a winning position to an equal one, or from an equal one, to a position that is still playable and basically equal, but for instance forfeits your initiative and thus will put you behind somewhat after your opponent moves. It would be like having the black pieces, though you are white. This isn't a move that results in any material loss either.

A blunder would be any move that results in giving you a losing position, even if both players continue with best play and or, if it results in loss of material, hence you will be behind, unless your play begins to exceed your opponents, until a point of equalization or better is reached.

People though often here use "blunder" and "mistake" interchangeably...I've given up even noticing or worrying about it anymore.

Blunder: pretty much every 3rd or 4th move I make ;-)

Blunder is a major mistake that with a little bit of closer attention could have been avoided and that in most cases is detected immediately at the magical moment when the move is made....

I like nameno s explanation and bronsteinitz definition.

My thing is: Is it a blunder if I eg. calculate incorrectly when it comes to exchanges and I end up being a pawn down or in a worse position after lets say 2 moves of exchanges? Or is this a mistake? Maybe it was not so easily seeable when I made the mistake.

I think Bronsteinitz definition comes closest to what I would say, but I am obviously not sure and namenos has good definitions of terms.

an inaccuracy is a "belch" move

a mistake is a "pants falling down" move

a blunder is an "i swam in crocodile waters without knowing" move

Blundering away, the moments that make up a chess day... who said that?

Andy, surely you weren't into world domination, a holocaust for women and a chess site without trysts ?

Whenever you are facepalming yourself, you have commited a blunder.

The rest is happy mistakes.

best definition yet!

As for the face palm....

I do that over little mistakes that force me to change my plans. I seem to usually have the right idea from a intuitive and strategic standpoint. I just get a bit confused in trying to make it reality sometimes.

+1

My, you blunder a lot!

Doing something after you do it  that you know was just plain dumb. A mistake is something that you may not have figured out before you did it, but once it is pointed out to you, then you see that what you did was wrong. 

Oh, one more thingy. The Chess.com analysis computer is just weird. 

I hate when I play all but flawlessly....and then a blunder ruins everything...lol