Sentence:  Since the launch early last year of ... two Silicon Valley start-ups offering free education through MOOCs, massive open online courses, the ivory towers of <WSD>academia</WSD> have been shaken to their foundations. University brands built in some cases over centuries have been forced to contemplate the possibility that information technology will rapidly make their existing business model obsolete. 
Meaning of the word marked with <WSD> tags:  The scientific and cultural community engaged in higher education and research, taken as a whole. (from 1956)