An online encyclopedia. This site is often not encouraged by schools due to the fact it can be edited by anyone with an account. Usually used when you have an argument about something with your friends and need to quickly get an answer to prove them all wrong.
Teacher: You get an E for your essay on pneumonoultramicroscopicsilicovolcanoconiosi! What da actual f*** kind of source did you use, peanut-brain?
Student: Wikipedia.
Teacher: YOU ACTUALLY USE FRICKIN' WIKIPEDIA?
A means of getting much needed information for most school-children, in order to put in as little effort required to complete a project due within several days.