Freeroll
A freeroll is a poker tournament that is free to enter but still offers real prizes. It also describes a situation in which a player can win the whole pot but cannot lose more than a split.
The simple explanation
Poker sites run freerolls to attract new players. You pay nothing to enter, and you can win money or a ticket to a bigger event. The second meaning is a hand in which you are sure to at least tie, and might win the whole pot, for example when two players hold the same pair and one has a flush draw.
A closer look
Freerolls are usually crowded, so the structure rewards patience and luck more than skill in the early stages. There are two main versions: public freerolls open to everyone, and password-protected ones for players of a specific site or club. In hand situations, a freeroll arises with a split: if you and your opponent hold the same made hand, and you also have a draw to a better one, you cannot lose the pot, but you can win it all.
A practical example
You hold A♠ A♣ against A♥ A♦. The board is 8♠ 9♠ 2♦ Q♠. You are freerolling: you can win the pot with a spade on the river, and otherwise you split it.
Full explanation
A freeroll is a poker tournament that is free to enter but still offers real prizes. It also describes a situation in which a player can win the whole pot but cannot lose more than a split.
A freeroll is a tournament with no entry fee that still has prizes. Many online sites offer them to new players.
It also means a position in a hand in which you cannot lose, because you at worst split the pot, but you can win all of it.
Outside poker, it describes any situation with no downside and some upside.
Freeroll fields are large, so deep runs need some luck.
Alternative spelling: free roll, free-roll