What does this group mean?

“Biting our thumb from people, cos Now i am a upset Shakespearean Bastard”
I do not understand the benchmark…

This is from Romeo in addition to Juliet, Behave 1, Field 1:

SAMPSON – “Nay, as they definitely dare.Let me bite my thumb from them;
that is certainly a disgrace to them, once they bear it.”.