A dead heat happens when two or more selections tie in a position where only one winner was expected, for example two players finishing as joint top scorers of a tournament.
In this case, your stake is divided by the number of tied selections. One part is paid out at your odds and the rest is settled as lost.
For example, you bet €10 on Player A to be top scorer at 6.00 odds, and Player A shares the title with one other player. Your stake is split in two: €5 wins at 6.00 (€30) and the other €5 is lost, so you receive €30 instead of €60.
Dead heat rules mostly apply to outright bets, golf, cricket, motorsport, and racing. In head-to-head markets, a tie usually means the bet is void and your stake is refunded.