In an entertainment context, "buzz" means the amount of popular discussion about a subject. This discussion is not by movie critics, but by people at large. Therefore, those measuring it cannot point to specific reviews or specific words; they measure "buzz," which is a representation of background noise.
Example: "There is a misconception that buzz will always transfer into sales," says Matt Smith, co-founder of the digital media and marketing company The Viral Factory, responsible for the viral campaign to launch the 2008 film Cloverfield."
Original story re: the next Batman film's viral marketing campaign here. .