Muck
The muck is the pile of discarded cards, and to muck a hand is to throw it in without showing it.
Once cards touch the muck they are dead and cannot be retrieved, even if it turns out they were the winning hand. That is why a player who has called on the river should always wait to see the other hand before releasing their own.
At a showdown you are only required to show if you want to claim the pot. Mucking a losing hand keeps information away from the table, and it is worth doing consistently rather than only when the hand was embarrassing.
an example
your cards
board
Your opponent turns over a pair of eights. Queen high loses, and there is no reason to show it, so the hand goes face down into the muck and nobody learns which hands you were calling with.
This example is made up. The real one is in your own hand history: find muck in your own hands and see how often it came up and what it cost you.
related terms
Fold
To fold is to give up your hand and any claim on the pot, which costs you nothing further and returns nothing you have a ...
Showdown
A showdown is the point after the final round of betting where the remaining players turn their cards face up and the be ...
Table image
Your table image is how the other players believe you play, which decides how they respond to your bets regardless of ho ...
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Knowing the word is not the same as seeing it.
The full order of play, from the blinds to the showdown.