What is a revelation?

In this verse it appears to be something that would show people what will take place. "...God gave him to show his servants what must soon take place..." Rev. 1:1

Dictionary.com says:

1. the act of revealing or disclosing; disclosure.
2. something revealed or disclosed, esp. a striking disclosure, as of something not before realized.
   
3. Theology.
   
   1. God's disclosure of Himself and His will to His creatures.
      
   2. an instance of such communication or disclosure.
      
   3. something thus communicated or disclosed.
      
   4. something that contains such disclosure, as the Bible.