user15365: I usually find in reports like this (and many others) something like:

... with a TPR of 2551 ...

I would like to know its meaning, and also what it stands for.

user12873: "Tournament performance rating". An approximate measure of the strength that a player performed/played at in the tournament.
The calculation of such a performance rating varies, but one method is as follows:

If you beat someone at rating X, your performance for that game is X + 400.
If you lose to this person, your performance for that game is X - 400.
If you draw this game, your performance for that game is X.

Then the tournament performance rating is calculated by taking the average performance out of all your games.

user924: It means Tournament Performance Rating.
Very roughly a TPR of 2551 means that the results this player has achieved in this tournament would have been expected of a player rated 2551.
That's always a bit problematic. Say you scored 100% against a group of 1500 players, what kind of player would have expected to score that? Well, a 1900 player probably, but also a 2800 player. And many methods make your TPR go down if you win against a much lower rated player, because they are based on the average rating of your opponents. But it's a rough measure of how well a player did.
There exist various methods to calculate it that I don't have time now to go into now.

15365: <p>I usually find in reports like <a href="http://www.chessgames.com/player/wei_yi.html" rel="noreferrer">this</a> (and many others) something like:</p>

<blockquote>
  <p>... with a <strong>TPR</strong> of 2551 ...</p>
</blockquote>

<p>I would like to know its meaning, and also what it stands for.</p>
 12873: <p>"Tournament performance rating". An approximate measure of the strength that a player performed/played at in the tournament.</p>

<p>The calculation of such a performance rating varies, but one method is as follows:</p>

<ul>
<li>If you beat someone at rating X, your performance for that game is X + 400.</li>
<li>If you lose to this person, your performance for that game is X - 400.</li>
<li>If you draw this game, your performance for that game is X.</li>
</ul>

<p>Then the tournament performance rating is calculated by taking the average performance out of all your games.</p>
 924: <p>It means <a href="https://en.wikipedia.org/wiki/Glossary_of_chess#Performance_rating" rel="noreferrer">Tournament Performance Rating</a>.</p>

<p>Very roughly a TPR of 2551 means that the results this player has achieved in this tournament would have been expected of a player rated 2551.</p>

<p>That's always a bit problematic. Say you scored 100% against a group of 1500 players, what kind of player would have expected to score that? Well, a 1900 player probably, but also a 2800 player. And many methods make your TPR go down if you win against a much lower rated player, because they are based on the average rating of your opponents. But it's a rough measure of how well a player did.</p>

<p>There exist various methods to calculate it that I don't have time now to go into now.</p>
