rdoc update.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@22697 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/securerandom.rb

@@ -215,7 +215,7 @@ module SecureRandom
     end
   end
 
-  # SecureRandom.uuid generates a v4 random UUID.
+  # SecureRandom.uuid generates a v4 random UUID (Universally Unique IDentifier).
   #
   #   p SecureRandom.uuid #=> "2d931510-d99f-494a-8c67-87feb05e1594"
   #   p SecureRandom.uuid #=> "62936e70-1815-439b-bf89-8492855a7e6b"