So what does it mean?! Put simply, it is saying that you are useless or a waste of time!
This Shakespearean insult is taken from The Merry Wives of Windsor (Act 1, Scene 1). Latten meant 'brass' and a bilbo was a 'sword' (because they came from Balboa in Spain).
The literal translation of this insult is: 'You brass sword!' A sword made of brass would be no use whatsoever, which is why this insult is so clever.
I like this insult becuase it is short and snappy, but you can also feel the anger of the speaker through the quick rhythms in the sentence.
