What does Nul mean?

As a nul she had to accept every drink from the older members that night.

Dutch student slang. This is a Dutch word. You will hear it a lot at Dutch universities, student associations and in student houses.

Some associations use nul instead of feut for someone who isn't a full member yet. You start at zero. Literally. After the introduction period you count. Also read about KMT and fresher.