Conspiracy: a secret plan made by two or more people to do something that is harmful or illegal
I got the definition form Merriam-Webster website. I encountered the word in the Ways of Seeing text on page 32. It says “By refusing to enter a conspiracy, one remains innocent of that conspiracy. But to remain innocent may also be to remain ignorant.” I understand better now that a conspiracy is a bad thing mainly but can be a useful thing because not being innocent means not being ignorant in this text.