When I first started in public relations, the definition I was taught was pretty straightforward - PR is about influencing your target audiences by leveraging the credibility of a third party. Basically, PR was media relations.
About 10 years later, I was introduced to the "Rose Analogy," which is a elegant way of verbally painting a picture about how PR works. The essence, though, remains the same.
Apparently, for some in the PR world, this is no longer sufficient. I'm hearing definitions that go on and on, seemingly making what is moderately complex downright incomprehensible. The Canadian Public Relations Society has now come up with:
Public relations is the strategic management of relationships between an organization and its diverse publics, through the use of communication, to achieve mutual understanding, realize organizational goals, and serve the public interest.
I don't agree with the definition. I think it's overly complicated. (Is "publics" a word? Does PR "serve the public interest?")
Lest anyone think this definition was hacked out by a couple of yahoos in no time at all, the process apparently began almost one year ago. You can read a bit about the process here.
Point is: PR was and always will be about getting the help of a credible third party in broadcasting your message to your audience.