1.NounA sheet of paper (or a digital analogue thereof) containing notes used to assist (with or without permission) on a test; especially, such a sheet used secretly and improperly.
"If you have trouble remembering all the trigonometric identities, the book has a cheat sheet in back that lists them."
2.NounAny summary or quick reference used as a shortcut or reminder, such as an aid for public speaking.