Fraud is the practice of getting questions through some means other than actual knowledge of the academic topic being asked. Common forms of fraud include making one-to-one cognitive maps between words and answers without having the slightest idea what the answer really means (e.g., "when I hear 'recoil' I say 'Mossbauer effect'") and memorizing binary-match lists. Getting an academic answer through trash knowledge is also considered a form of fraud.
Calling "fraud" is a judgment on the player, not the question; even the best-written academic questions can be subject to fraud. However, questions which encourage fraud by containing a lot of Nobel Prize clues or trash in academic subjects are worthy of damnation, and are usually referred to derisively as fraudable questions. Fraud is common in questions that name drop.
Reverse fraud is a less-commonly used term for the practice of getting a trash question through academic knowledge, usually because of the whimsical inclusion of an academic-type clue. For example, a question on the moon of Endor from Star Wars that contains an allusion to the Witch of Endor from the Bible is open to a reverse fraud buzz.