what you call someone from belgium. really. there is no other term.
Mr A: "hello there, may i enquire as to what is your country of origin?"
Mr B: "why yes, i am from belgium."
Mr A: "just to clarify, does this make you belgiumish or belgiumise?"
Mr B: "of course it makes me of the belgiumish nationality. belgiumise? don't let's be silly now..."
The incorrect way of spelling belgiumise , which is the incorrect way of saying your belgian (but its cool so who cares)
mr t, hi what nationality are you?
miss k, im belgiumish
mr t , hmm are you sure thats right?
miss k, Whoops i meant to say belgiumise
mr t, its ok