David Robertson 
Routledge Dictionary of Politics [PDF ebook] 

This dictionary is the essential guide to politics, its terminologies, ideologies and institutions. Providing authoritative and up-to-date information that is invaluable to both students and general readers, it includes: well over 500 extensive definitions an understanding of the basics of political thought and theory clear, no-nonsense coverage of complex ideologies and dogmas succinct definitions of highly specialized and technical terms. Previously published by Penguin, this third edition has been extensively revised and updated with many new entries.