the verb would be "отлучать от церкви". But it's true that it's diffucult to translate this really close enough due to different practices. It's clear that excommunication in an Amish community results in something different if compared to excommunication in Russian Orthodox (consequences and impact on the person involved would be different).
On a similar note, it reminds me of a famous Russian writer Leo Tolstoy. In Russian texts it is usually said that he was "предан анафеме" (Greek word is used here, which means he was officially damned by the Russian Orthodox Church for his ideas on Christianity and large discrepancies of his life views with the Russian Church, definitetly he was not 'shunned', i don't know if 'shunning' is ever practiced in the Russian Orthodox Church, cos it seems to contradict to evangelical ideas).
In the wikipedia artical about Leo Tolstoy though the word 'excommunication' is used: After Anna Karenina, Tolstoy concentrated on Christian themes, and his later novels such as The Death of Ivan Ilyich (1886) and What Is to Be Done? develop a radical anarcho-pacifist Christian philosophy which led to his excommunication from the Russian Orthodox Church in 1901.