The Second Negative Rebuttal (2NR) is the fourth speech given by the negative team, the seventh speech in the debate, given by the second negative speaker.
The 2NR will often take the remainder of the negative's preparation time.
The 2NR will usually only go for some of the arguments presented in the 1NC although community norms prevent it for going for 1NC arguments which were not extended in the negative block. Especially in rounds with experienced debaters, the 2NR will usually try to win the round with as few arguments as possible enabling it to effectively cover all relevant 1AR arguments while gaining a substantial time trade off. However, sometimes the 2NR will go for multiple positions, allowing it to win the round in multiple worlds, if it believes it can effectively pressure the 2AR. This is risky because the 2AR, in that situation, will most likely go for the arguments which the 2NR covered the least.
The 2NR also has to "close doors" for the 2AR by predicting the areas in which the 2AR will attempt new extrapolation. The 2NR can caution the judge to reject new 2AR arguments but this is less effective than preempting such arguments with "even if" statements.
Read more about this topic: Structure Of Policy Debate