A small piece of paper, usually printed on with a very tiny font, used to store useless information required to pass a pointless exam. Not needed for useful exams, since you usually already know all the answers to those.

One great way of making a cheat sheet is to sharpen the point of a mechanical pencil (by scribbling sideways with it beforehand) and writing very lightly. You can usually cram lots of information on a small piece of paper this way. In some cases, you may put so much time into making a cheat sheet that by the time you are done, you've managed to memorize everything and won't need it at the exam!