What is calumny? (From Shakespeare's Hamlet)

Slander; a misrepresentation intended to blacken another's reputation.

If thou dost marry, I'll give thee this plague / for thy dowry: be thou as chaste as ice, as pure as / snow, thou shalt not escape calumny. Get thee to a / nunnery, go; farewell.

Hamlet, from Shakespeare's Hamlet; Act III, Scene 1.