IPA: /ˌɛkjuˈmɛnɪsɪst/
KK: /ˌɛkjuˈmɛnɪsɪst/
A person who supports or promotes the unity and cooperation among different Christian denominations.
As an ecumenicist, she worked tirelessly to bring together various churches for joint services and community projects.
Ecumenicist → It is formed from "oikoumenē" (Greek, meaning the inhabited world) and "-ist" (meaning a person who practices or is concerned with). An ecumenicist is a person who is concerned with promoting unity among different Christian denominations and, by extension, among all religions.
Think of someone who is focused on the 'inhabited world' ('oikoumenē') and works towards unity among various faiths — that's what an ecumenicist does.