When you mock someone and make fun of him, this is an example of how you denigrate him.
The movie critics denigrated the director's latest film.
Origin of denigrate
- Latin dēnigrāre dēnigrāt- to blacken, defame dē- de- niger nigr- black nekw-t- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition
- From Latin dēnigrātus, the past participle of dēnigrāre (“to blacken”), from dē + nigrare 'to blacken (from niger (“black”))