What is a zerbert?

A zerbert is the act of touching lips on the skin of another person and exhaling in a way that makes a loud fart-like sound. It's likely that zerberts have been performed for as long as humans have evolved from the apes as a species with smooth enough skin to perform the task, but the term was popularized in the United States during the 1980s on a The Cosby Show, a popular 30-minute comedy that aired on the NBC television network. Most typically, adults perform zerberts (or zerbert someone, to use the term as a verb) on children in order to make them laugh.