what does it mean by define the bureaucracy as “a large, complex organization composed of appointed officials.” ?

Answer 1

http://www.answers.com/bureaucracy

There's a very complete definition. I don't understand your assignment, though. Are you to write a complete definition of the term "bureaucracy"?

Here's help for writing a definition essay:
http://grammar.ccc.commnet.edu/grammar/composition/definition.htm

http://owl.english.purdue.edu/owl/resource/622/01/

http://www.northland.cc.mn.us/owl/Doing%20the%20definition%20essay.htm

http://essayinfo.com/essays/definition_essay.php

One thing to avoid is a definition straight from any dictionary in your introduction or thesis statement!