The terms bankrupt and prodigal are used in Act 3, scene 1 by Shylock the Jewish moneylender, when he refers to Antonio, a Christian merchant and also our protagonist.
Shylock has been conversing with Salarino and Salanio, two of Antonio's Christian friends, about his daughter, Jessica, who has eloped with Lorenzo, a Christian. Shylock is very upset about his daughter\s betrayal and the fact that she had also stolen some of his valuables. During their conversation, Salarino asks Shylock:
tell us, do you hear whether Antonio have had any
loss at sea or no?
The reason why Salarino asks Shylock this question is because the Jew and Antonio share a common interest. Shylock had lent Antonio's friend, Bassanio, three thousand ducats and Antonio had signed a bond that the loan would be repaid within three months. Rumors had been circulating that Antonio had lost all his ships at sea and would, therefore, not be able to settle the debt. Shylock would, of course, be very interested in this news since he had vowed to avenge himself against Antonio's abuse and this would give him the ideal opportunity to do so legally since the bond stated that he could cut out a pound of Antonio's flesh if he should forfeit on the agreement.
It is then that Shylock says:
There I have another bad match: a bankrupt, a
prodigal, who dare scarce show his head on the
Rialto; a beggar, that was used to come so smug upon
the mart; let him look to his bond:...
Shylock here compares Antonio to his daughter, Jessica, who he feels has betrayed him and, in a similar manner, Antonio is a bad partner since he cannot fulfill his duty of repaying the bond. The reason for this is that Antonio is a bankrupt, which is a term used to refer to someone who is unable to repay his or her debts. Such a person does not have the resources to settle a debt and therefore a court has to intervene to ensure that such a person's creditors can have at least some restitution.
Shylock also calls Antonio a prodigal which refers to a person who is wasteful and extravagant. He believes that Antonio was irresponsibly lavish and generous and should, therefore, be punished for his indiscretion. Shylock lodges a malicious suit against Antonio and asks the duke to make a judgement against him for not honoring his obligation.
Shylock's malice lies in the fact that he hates Antonio for he is a Christian and also that he had suffered abuse at Antonio's hands, who had sworn at him, kicked him, called him a dog, criticized his lending practice and spat him on his cloak and in his face.