What does extermist mean?

If you mean "Extremist"

American Heritage Dictionary - Cite This Source - Share This ex·trem·ist (ĭk-strē'mĭst) Pronunciation Key

n. One who advocates or resorts to measures beyond the norm, especially in politics.

ex·trem'ism n., ex·trem'ist adj. * http://dictionary.reference.com/browse/extremist