Use the adjective tonsorial when you need a fancy way to talk about barbers. Want to cut hair when you grow up? Tell your parents you're going into the tonsorial field.
Even though tonsorial sounds like it has something to do with tonsils, the words are completely unrelated. Tonsorial comes from the Latin tonsorius, "of or pertaining to shearing or shaving." You're most likely to encounter this adjective in a humorous or overly formal context, and it can describe anything that has to do with cutting hair or shaving.