In "Romeo and Juliet," why does Samson bite his thumb at two of Montague's servants?The question is from romeo and juliet

Samson bites his thumb at the Montague's servants because in that time it was a gesture of insult.  Rather like "flipping a bird" is in our society or other hand gestures in other cultures are used to indicate insult, anger, and perhaps an invitation to violence.

Samson and Capulet servants like him would have taken on their master's feuds as if they were their own.  So, the feud would be fought from the highest head of the family to the lowest servant of one family against the same for the other family in question.

Check out the links below to help you understand gestures and their meanings in different cultures and time periods.