Final answer:
Buzz is the term that defines the exponential expansion of word-of-mouth, often related to how products or events become popular through personal endorsements shared among people.
Step-by-step explanation:
Buzz is defined as the exponential expansion of word-of-mouth. This term often relates to marketing strategies where products, services, or events gain popularity through the process of people sharing information. This can occur both online and offline and typically involves an element of virality. Buzz can be particularly powerful because it comes with the implication of personal endorsement, making it a highly sought-after outcome for businesses and marketers trying to spread the word about their offerings.