(Latin: calvor, to use artifice, deception)
Any deception of another, especially in judicial matters, commonly used to mean unjust damaging of another's character by imputing to him something of which he is not guilty.
It is an act which varies in sinfulness according to the gravity of the fault or crime imputed and the damage done.
It calls for retraction and for reparation of the damage done, provided this had been foreseen.
In canon law, the oath taken to attest that the litigation on both sides is in good faith is called juramentum calumnire (oath disclaiming calumny).
New Catholic Dictionary