IPA: /ˈtʃælɪndʒər/
KK: /ˈtʃælɪndʒər/
A person or thing that competes against someone or something, especially in a contest or competition.
The challenger stepped into the ring, ready to fight for the championship title.
Challenger → It is formed from "challenge" (from Old French *chalenge*, meaning to accuse or call to account) and "-er" (meaning a person who). A challenger is a person who calls someone out or contests something.
Think of someone who 'calls out' or 'accuses' another — that's what a challenger does.