The contemporary definition for black humor is given thus, 'In literature and drama, combining the morbid and grotesque with humor and farce to give a disturbing effect and convey the absurdity and cruelty of life.' In simple terms this would mean to make light of a serious or tragic situation by joking about it to illustrate how foolish life can sometimes be.
In Act lV, scene lll, Hamlet is making fun by using a pun—a play on words for humorous effect—when he refers to where Polonius' body might be found. Claudius wants to know what the prince has done with the body and Hamlet says that Polonius is 'at supper.' Obviously, since Polonius is dead, he cannot be the one who is eating. Hamlet therefore means that Polonius is being eaten. His rotting corpse is being devoured by maggots. The 'supper' he speaks of is, therefore, the feast enjoyed by the maggots.
Hamlet calls these maggots a 'convocation of politic worms.' He, once again, uses ambiguity to make a point and jest about Polonius' corpse. The word 'politic' alludes to Polonius' political position. In life, he was the king's chief adviser and Hamlet's remark actually suggests that the worms, in ingesting Polonius' flesh, are acquiring his political attributes. Furthermore, the word also means 'wise' and 'judicious' and in this context, it would mean that the worms are doing something sensible and desirable, much as politicians are supposed to do - make intelligent decisions for the benefit of all. There could also be another meaning which implies that getting rid of the body is the best thing the maggots could have done. They got rid of something rotten and irrelevant, an imbecile, because Polonius paid with his life for his foolish obeisance to the king.
The word 'convocation' suggests a meeting. This ties in with the political theme of Hamlet's mockery. The maggots have, in essence, come together to fulfill a common purpose, which is to get rid of Polonius' body and, at the same time, benefit from the nourishment it provides. The metaphor is extended when Hamlet also mentions that in life, we fatten other creatures to feed us and, in the process, we fatten ourselves to be feasted on by maggots. The suggestion is that, in the end, the entire exercise is a purposeless one because we all eventually end up being nothing more than fodder for worms to feed on.
In addition, Hamlet later also suggests that ones lofty position means nothing in the greater scheme of things since a king can be eaten by worms which are later used as fish bait and the fish, for its part, can be consumed by a beggar. So, no matter what titles or grand authority we might have had in life, we are humbled in, and after, our demise. When he makes this remark to Claudius, he is obviously insinuating that Claudius should be aware of how unimportant title or authority is within this context.
Hamlet's humorous repartee and mockery emphasizes how much he actually despised the now deceased Polonius. He had been making fun of the almost servile attitude Polonius had adopted. Hamlet deemed him an idiot worthy only of his ridicule. His derision for the man does not end when Polonius dies but continues after his death. Because Polonius was Claudius' dutiful servant Hamlet has, in effect, projected his utter contempt for the king to all who serve him. He does the same with Rosencrantz and Guildenstern.
In Act IV, Scene 3 of Shakespeare's most famous play, Hamlet, the black humor of Hamlet's comments about the dead Polonius stem from his treatment of the serious issue of death in a farcical manner, ridiculing Polonius, whom Hamlet has found repugnant in his sycophantic and hypocritical ways. In a broader sense, Hamlet conveys with his dark humor the paradox of life, an existence so revered by many, yet one that ends so insignificantly.
This black humor of Hamlet's begins when King Claudius asks the prince where Polonius is, and Hamlet replies that he is "at supper," not meaning that the man is eating a meal, but that he himself is "supper" for the worms.
Not where he eats, but where he is eaten. A certain
convocation of politic worms are e'en at him. Your
worm is your only emperor for diet. We fat all creatures
else to fat us, and we fat ourselves for maggots. Your fat
king and your lean beggar is but variable service, two
dishes, but to one table. That's the end. (4.3.22-27)
In these lines, Hamlet describes Polonius's end as well as that of the king and the beggar, who after death are equalized in their insignificant "end" as they all become part of the food chain.