Sentence:  The hallmark of the late twentieth century in the media industries (and adjacent/overlapping territories, such as the Internet) was the weakening of boundaries that previously distinguished arenas, enterprises, institutions, and professions. ... Entertainment media—the rapidly <WSD>conglomerating</WSD> TV/film/cable/publishing/music/sports/Internet megasauruses that can be seen grazing in Los Angeles and New York—represent the pattern even more dramatically than in the case of journalism. 
Meaning of the word marked with <WSD> tags:  To combine together into a larger corporation.