A self-destruct, often abbreviated SD or referred to as suicide, is the term for when a character gets KO'd without being hit by opponents in the Super Smash Flash series. A self-destruct may occur to a player in Super Smash Flash if they touch the stage's blast line without first being hit in the air or into the blast line, while in Super Smash Flash 2 it only occurs if the KO'd player was not hit last by an opponent during the stock. It may also occur if the player gets KO'd by a stage hazard.
Each self-destruct subtracts one point from the player's score. While Super Smash Flash counts each self-destruct as a fall (only the falls are included in the score), Super Smash Flash 2 counts self-destructs and falls separately.
Super Smash Flash includes two bonuses related to self-destructs: "SD's", which penalizes 500 points for every self-destruct the player commits, and "Self-Destructor", which penalizes 2000 when player has a lot of self-destructs.