A tip, or gratuity, is a small amount of money given voluntarily as a token of appreciation for a service rendered. According to Webster's Dictionary, the word "tip" is also considered by many to be an acronym: T.I.P. - "To Insure Promptness" or "To Insure Prompt" service. We tip our servers as a way of thanking them for good service. We might also leave a very low tip, or no tip at all, as a signal that the service was terrible.