The word cabrón refers to a cuckold, a man whose wife or girlfriend has been unfaithful without his knowing about it. Although the word also means ‘male goat’ and is inoffensive in that context, when used in slang, it can be extremely insulting or offensive. The word also has several other meaning in current slang.
Although the idea of being cheated on by a woman is uncomfortable for men around the world, it is particularly unpleasant in Latin culture, so the word cabrón should be used with caution, and only when you are very comfortable and confident with it. (http://www.languagerealm.com/spanish/cabron.php)
"The information his secretaries continually gave him about Carranza confirmed him in his notions: there northern First Chief, so went reports, was a thieving, ambitious old cabrón, surrounded by conniving lawyers indifferent to the miseries of common people."
- John Womack, Zapata and the Mexican Revolution