A lightning round is a category round read on a sixty-second clock, which requires teams to manage their response time in order to hear as many questions as possible. After time expires, questions which were fully read and not answered correctly by the first team may bounce back to the second team off the clock.
Though many bad quizbowl events use a lightning round (including the NAC, which calls it a 60-second round dubiously claims that Mike Mastandrea invented it), the presence of a lightning round is not inherently a marker of bad quizbowl. The third quarter of National History Bowl is a lightning round.
The origins of the lightning round may date back to It's Academic (1961), which, in its original format, consisted primarily of lightning rounds, albeit with several differences, such as point penalties for wrong answers, a smaller penalty for passing a question (but that allowed the other teams to attempt the question at the end of the round), and being able to answer a question interrupted by the timer after the timer sounds.
The NAC once included a sixty-second round of ten six-second audio clips, which meant that it was mathematically impossible for the first team to hear and answer all ten questions.