n. A pundit or commentator who speaks in a loud voice and whose comments tend to be abrasive, aggressive, and partisan.
Try finding a discussion of these issues on any news network. The barking heads who usurp the space of public affairs with high-volume jeers are not equal-opportunity offenders.
The sports anchor desk jockeys are still, by and large, a good-looking, well-coiffed bunch of guys. … They're still LOUD, in the age-old tradition of assaulting your eardrums with headline-shrieking staccato sentences. … But, in fact, there is something new going on here. … The barking heads have been nurturing personal styles whose only shared quality is a kind of evangelical furor.
This phrase (spied by subscriber Laurie Mullikin) appears to have been coined by several people over the years. For example, it was self-coined (self-coin: "To coin an already existing word that you didn't know about.") by Laurie in 1997 and by Todd Gitlin in 1998. However, the actual first use goes back to 1988.