I was watching a movie and then when he took out this bucket which i think is to puke in, he said 'Verkotzer'. Checked it up on a dictionary and the internet, but couldn't find it. Is this some sort of slang or?
It would be helpful to see and hear that scene. But generally, the dictionaries only counts common words. But people does 'play' with their language and creating new 'one time words' for the moment. Sometimes those experments become common and regular words, when more and more people uses this new creation.
So it may have been in fact "Verkotzer", but it depends on the situation and could be understand only with in there. This is definitively not a common german word.
That's the first time I saw this word. I can only guess. There is a word "Vorkoster". That is a person who professionally tastes the food before a more important (or rich) person eats it. That is to check whether the food is poisoned.
I think it is just the simlilarity between "Vorkoster" and "Vorkotzer", so the Vorkotzer checks out if it is safe to vomit.