Boop

A boop is the act of lightly tapping someone's nose. The person being booped may playfully cover their nose or make a comedic "squeek" sound. It is often performed on fursuits, but can also be used in online role playing sessions. The term is derived from the word bop.

As with most actions, it is best to ask someone before booping them (unless you already know if they are okay with it).