What does Ibu mean?

Before going to bed, she took an ibu just in case.

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

Lots of students grab one the day after going out, ideally with a big glass of water. The other classic is para, short for paracetamol. Neither one fixes a brak Sunday completely though. Also read what hangover means.