IPA: /ˈsɛkjʊlərɪst/
KK: /ˈsɛkjələrɪst/
A person who believes in or supports the idea that religion should not play a role in government or public affairs.
The secularist argued for the separation of church and state in the education system.
Secularist → It is formed from "secular" (from Latin "saecularis", meaning worldly or temporal) and "-ist" (meaning a person who practices or advocates). A secularist is a person who advocates for a separation from religious influence in public life.
Think of someone who is focused on the 'worldly' ('secular') aspects of life rather than religious ones — that's what a secularist does.