In an article the author wrote "Langone is no slouch as a trash talker, but this was simply juvenile." I don't understand the meaning of "is no slouch as a trash talker".
No slouch - an understated way of saying someone is good at something.
She's no slouch as a housekeeper - She keeps her house in nice shape.
Trash talk - Usually applies to athletes, or other rivals, and sometimes in good humor and sometimes quite mean, putting down the skills and abilities of the others and building up your own.
In total, he was good at that type of talk, saying how good he (and his team?) are and how much they are going to dominate the other person (or his team).