Searched wiktionary but seems none of the explanations in it makes sense.
You'll want to look up the term break bad:
(colloquial, southern US) to go wrong, of people or events, including to turn toward a life of crime or immoral activity
The title of the series is a play on the phrase.
break : (copulative, informal) To suddenly become.
Things began breaking bad for him when his parents died.
The arrest was standard, when suddenly the suspect broke ugly.