user3890: A miniature is a short game of chess. Depending on the forums you ask in or the blogs you look at, the length of the miniature is always a problem.
Is there a standard number of moves under which the game is considered to be a miniature? Is there a reason that number is special?
Not even Wikipedia has a concrete definition regarding this aspect of the game.

user4418: If you are talking about the embarrassment of losing in so few moves that it counts as a miniature then the answer is 20.
If you are trying to scrape together as many short games as you can then the answer is 30, but the one that really counts, that really hurts is the 20 move one.

user4130: The answer, as hinted in the other comments, is that there isn't a solid definition. Unlike @Mikhail Tal's answer, though, the number I had always head was 20 moves (40ply) or thereabouts. 
Those who are familiar with 30 as a boundary might think of this as too short, but as an example the "Opera Game" was only 17 moves and the "Immortal Game" for all its action was only 22. I would posit that the reason that books like 500 King's Gambit Miniatures use 30 as a boundary is simply because there probably aren't enough games under 20 that are off worthwhile quality and that a potential reader hasn't already like seen.

user3405: I have an old book in my house, 500 King's Gambit Miniatures, and in the first pages the games, at the least, didn't pass 30 moves. I think it is a very good definition.

3890: <p>A <a href="http://www.chessgames.com/perl/chessgame?gid=1012733" rel="noreferrer">miniature</a> is a short game of chess. Depending on the forums you ask in or the blogs you look at, the length of the miniature is always a problem.</p>

<p>Is there a standard number of moves under which the game is considered to be a miniature? Is there a reason that number is special?</p>

<p>Not even <a href="http://en.wikipedia.org/wiki/Glossary_of_chess#Miniature" rel="noreferrer">Wikipedia</a> has a concrete definition regarding this aspect of the game.</p>
 4418: <p>If you are talking about the embarrassment of losing in so few moves that it counts as a miniature then the answer is 20.</p>

<p>If you are trying to scrape together as many short games as you can then the answer is 30, but the one that really counts, that really hurts is the 20 move one.</p>
 4130: <p>The answer, as hinted in the other comments, is that there isn't a solid definition. Unlike @Mikhail Tal's answer, though, the number I had always head was 20 moves (40ply) or thereabouts. </p>

<p>Those who are familiar with 30 as a boundary might think of this as too short, but as an example the "Opera Game" was only 17 moves and the "Immortal Game" for all its action was only 22. I would posit that the reason that books like <em>500 King's Gambit Miniatures</em> use 30 as a boundary is simply because there probably aren't enough games under 20 that are off worthwhile quality and that a potential reader hasn't already like seen.</p>
 3405: <p>I have an old book in my house, 500 King's Gambit Miniatures, and in the first pages the games, at the least, didn't pass 30 moves. I think it is a very good definition.</p>
