RADICAL

 [edit] Pronunciation

• enPR: rădʹĭk-əl, IPA: /ˈɹædɪkəl/, SAMPA: /"r{dIk@l/
• Homophones: radicle

[edit] Adjective

radical (comparative more radical, superlative most radical)

1. Favoring fundamental change, or change at the root cause of a matter.   His beliefs are radical.
2. (botany, not comparable) Of or pertaining to a root (of a plant).
3. Of or pertaining to the intrinsic nature of something.
4. (slang) Excellent.   That was a radical jump!

 http://en.wiktionary.org/wiki/radical