I recently attended a conference at which the topic of "public intellectuals" came up. I refrained from offering my dyspeptic views on the topic because doing so would have disrupted the congenial atmosphere. But now, triggered by another's blog post, I can offer my entry for Ambrose Bierce's Devil's Dictionary (though without, I admit, Bierce's wit):
Public intellectual:
A person, ordinarily with a university appointment, who spouts off at
semi-regular intervals on a range of topics about which he or she has varying
degrees of knowledge and expertise, in terms that lead readers who already
agree with the point of view expressed to acknowledge the author’s insight.
[It has not escaped my attention that one might regard this as a self-referential blog post.]