Biting one's thumb is a gesture of ill will. Sampson of the Capulets bites his thumb when Abram, a Montague, walks by. Sampson cannot admit to biting his thumb AT Abram, as such an act is a call to fight, and the prince has forbidden the houses to fight. Sampson, therefore, contends that he is simply biting his thumb for no reason and that Abram has misinterpreted the action.