Donk bet
Leading into the previous street's aggressor from out of position. Named as an insult — and a real weapon on the boards that hit your range harder.
You defend the big blind against a button open. The flop comes 7-6-5 with two hearts and you bet into the raiser before they have acted. That is a donk bet, and the name is a leftover: for years it was the signature of a bad player who did not understand that the aggressor bets and the caller checks.
The reason it became respectable is range structure. A button opening range is full of big cards; a big blind defending range is full of middling and connected ones. On 7-6-5 the caller's range contains far more two pair, sets and straights than the raiser's, and on that board it is the caller who should be betting. The rule is not "never lead" but "lead on the boards your range hits and theirs does not" — low connected flops, paired low boards, and the occasional monotone card that pairs your defending suits.
Used that way it also solves a real problem: checking every flop hands the initiative to a player who will c-bet almost everything, and defending against that from out of position with a capped range is the least pleasant position in poker.
The mistake is the original one, which is why the name stuck. Leading with top pair on an ace-high flop, into a range built out of aces, is a bet that folds out everything you beat and gets called by everything you do not. If your range is the weaker one on that board, checking is not passive — it is the only thing that keeps your strong hands hidden inside it.
FAQ
What is a donk bet in poker?
A bet made out of position into the player who raised on the previous street, before they have had a chance to continuation-bet. The name comes from donkey, because it was long considered a beginner's mistake.
Is donk betting ever correct?
Yes, on boards that connect with the caller's range far better than the raiser's — low connected flops like 7-6-5, and paired low boards. There the caller holds more two pair and sets, so leading is both a value bet and a defence against automatic continuation bets.
What is the difference between a donk bet and a probe bet?
A donk bet leads into an opponent who still has the betting initiative. A probe bet comes after they have given it up by checking back the previous street, which caps their range and makes the bet far safer.