Sentence:  [http://books.google.com.au/books?id=ii6bZwEACAAJ&dq=%22trifecta%22%7C%22trifectas%22+-intitle:%22%22+-inauthor:%22%22&hl=en&sa=X&ei=7QWZUIWVC4memQWG0IDICQ&redir_esc=y The <WSD>Trifecta</WSD> of Evil and the Crisis of Faith: Devil, Satan, and Lucifer] 
Meaning of the word marked with <WSD> tags:  A set of three related things, often things that cause problems.