Interrupt penalty
The practice of giving a penalty, usually minus five points, to a player who has interrupted the question with an incorrect answer.
Negs are used in all forms of collegiate quizbowl, including NAQT and ACF; in all College Bowl Company games, including College Bowl and HCASC; and in most forms of high school quizbowl. Some exceptions at the high school level include the PACE NSC format, Illinois Scholastic Bowl, and the OAC format.
In all known formats which use the 10/-5 style of negs, they only apply when the wrong answer is given by the first team to buzz on the question and the question has not yet been completed; if the question is over, or the other team is buzzing after the first team has already negged, or both, then there is no penalty for a wrong tossup answer.
It's Academic and Panasonic use a different system, in which the entire value of the tossup is lost by answering incorrectly at any time, and the other teams are not allowed to buzz on that question.