Note that you cannot ask a question by saying 'What means...?'. Your question should be this: "What does icing mean?'
The word order for questions is as follows:
Question word = What
Auxiliary = does
Subject = 'icing'
Main verb = mean?
If you ice a cake, you put a sweet sugary layer on top of it. This topping is called icing. I can't think of a situation where 'icing' would mean a plastic object.