The poker term donkey is a demeaning way of calling a player unskilled, unknowledgeable, and overall a very bad player. Donkeys typically have a loose and aggressive playstyle accompanied by a lot of mistakes.
Donkey Poker Example:
One of the most common signs that a player is a donkey is if they are overplaying hands with low winning odds. For instance, they might play an 8 2 or 9 2 offsuit hand rather than folding, which is something experienced players would recommend doing.