IPA: /ˌsɛɡrɪˈɡeɪʃənɪst/
KK: /sɛɡrɪˈɡeɪʃənɪst/
A person who supports or promotes the separation of different racial or ethnic groups, often in a social or political context.
The segregationist policies of the past have had lasting effects on society.
Segregationist → It is formed from "segregare" (from Latin, meaning to separate) and the suffix "-ist" (meaning a person who practices or advocates). A segregationist is a person who advocates for the separation of groups, particularly in social or racial contexts.
Think of someone who 'separates' ('segregare') groups and is an 'advocate' ('-ist') for that separation.