Is it possible to loose a game without mistakes by checkmate ?

ok, we are getting off topic, lets get back on topic, isn't there that one book move checkmate on chess.com

It actually is possible. For the fool's mate all the moves are book moves

And blackmer gambit

like this

#51

8 d5 is a pretty refutation
Black certainly did not play without any mistake
3...Bc5 develops the bishop before the knight: 3...Nf6 or 3...a6
4...Bb6 moves the same piece twice in the opening
5...exd4 cedes the center, trades a central pawn e5 for a wing pawn c3, freeing square c3 for Nb1
6...Nce7 moves the same piece twice in the opening

What about brilliant move.

#59
A brilliant move is just a good move with some aesthetic appeal.

Not really, from what I understand, a brilliant move is a move that is only good if you play a specific line in the next few moves.

Here is a more sensible definition of a brilliant move:

1) It is a move that wins: drawing or losing moves are not brilliant
2) It is a unique move: when several moves win, none are brilliant
3) It involves a scarifice: aesthetically pleasant
4) It is a quiet move: no check or capture: those are too obvious

well, I recently played a -game- EDIT: move that was brilliant, that was a check, so 4 is out, 3 is common, but to my knowledge, is not required, and also, for 3b, that's subjective, for 2, unique is vague, things can be unique in different ways, and for 1. what if its a move that seemingly weakens your position but actually causes a draw if you play a specific line.

I am going off the chess.com engine definition, which isn't necessarily the best, but that's what I'm going off of, now if we are talking about a human's definition, that's a different thing entirely.

#62 number 4 is wrong. I got a brilliant move which was a check

Flagging

Plot Twist/Possible Option: Your opponent just resigned before you played a move

Resigning, flagging, answering a cell phone during the game and getting forfeited, etc. are ways you can lose while not playing any bad moves, but the OP's topic was specifically "lose by checkmate" (well, loose, but lose was obviously what was meant).

This question has long fascinated me because often when I lose, I am convinced that I didn't make any mistakes. Here is a game that I resigned in a clearly lost position, but according to chess.com computer analysis, I played zero blunders, mistakes or inaccuracies.

1. d4 d5

2. c4 c6

3. Nf3 e6

4. e3 Nf6

5. Nc3 Bd6

6. Bd3 h6

7. 0-0 0-0

8. cxd5 exd5

9. Qc2 Re8

10. Re1 Bg4

11. e4 dxe4

12. Nxe4 Nxe4

13. Bxe4 Nd7

14. Bd2 Nf6

15. Bf5 Bxf3

16. gxf3 Qc7

17. h3 BF4

18. Bxf4 Qxf4

19. Be4 Nxe4

20. fxe4 Re6

21. Re3 Rg6+

22. Kh1 Re8

23. Rg1 Rxg1+

24. Kxg1 Re6

25. Qd3 b5

26. b4 Rg6+

27. Rg3 Rxg3+

28. fxg3 Qc1+

29. Kf2 Qb2+

30. Kf3 Qxa2

0 - 1

I've put the game into the analysis tool here, and that is the result. I will show some obvious bad moves as well.

Just to add however, the position in the end is probably a draw according to the engine, sure black is better, a pawn up and with seemingly a more active queen, but if some pawns get traded off, queen vs queen and a pawn is really difficult to win. And except for b4, it is not easy to target white's pawns. That being said, in a practical game, I admit that I could easily lose this game (from both positions because I am a patzer), but the engine says -0.3 or something.

As for the game itself, here are some mistakes:

This is all theory actually, I may have the move order wrong but this is all book moves.

Sure, but you can't say there are no mistakes in that game.