An extra question, usually on a test, that serves one of the following purposes:

1. To help a class whose grades are hopeless, often because of the ineptness of the teacher. Example: What is 2 + 2?
2. To anger a class that insists on a "good" bonus question (like the one above), probably because they think their grades are hopeless. Example: What is the resonant frequency of a chicken's skull?
3. To prove a point to students. Examples: What is the sum of the integers between 1 and 100? What is the full name of the author of this course's book?
4. To have at least one question on the test that the A students won't get right, without hurting the grades of everyone else. Example: Is hell exothermic or endothermic?