IPA: /ˌɪrɪˈlɪdʒənɪst/
KK: /ɪrɪˈlɪdʒənɪst/
A person who does not follow or believe in any religion.
As an irreligionist, she often questioned the beliefs of those around her.
Irreligionist → It is formed from "ir-" (meaning not) and "religion" (from Latin "religio", meaning to bind or tie back) and "-ist" (meaning a person who practices or is concerned with). The word refers to a person who does not adhere to or practice religion.
Think of someone who is 'not' ('ir-') 'bound' ('religio') by religious beliefs — that's what an irreligionist is.