We celebrate as Open Access gains momentum in the scholarly world while recognizing that the concept of Open Access is not understood by everyone. My favourite definition of Open Access comes from Peter Suber:
Open-access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions.
That's the short-version. You can find the longer version on Peter's website along with important elaboration such as:
OA is compatible with copyright, peer review, revenue (even profit), print, preservation, prestige, quality, career-advancement, indexing, and other features and supportive services associated with conventional scholarly literature.
And if you would like to read the considerably longer version, the Leddy Library has a copy of Peter Suber's book (which will be released as Open Access in June 2013 - one year after it's publication by MIT Press). The Leddy Library has other readings on Open Access and the changing nature of scholarly communication in the networked age and a list of six such titles can be found online.