radical

rad·i·cal [rad-i-kuhl] Show IPA 
adjective 
1. of or going to the root or origin; fundamental: a radical difference. 
2. thoroughgoing or extreme, especially as regards change from accepted or traditional forms: a radical change in the policy of a company. 
3. favoring drastic political, economic, or social reforms: radical ideas; radical and anarchistic ideologues.

adapted from :http://dictionary.reference.com/browse/radical