What does Grondpizza mean?

Leaving the club, they had to watch out for a stray grondpizza.

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

You see them outside clubs at the end of a night. The term is also used when it lands in a urinal instead of on the floor. Eating well before you go out, or bodem leggen, helps you avoid making one. Also read about grondpannenkoek and barf.