a person who participates in competitions
"The nervous contestant took a deep breath before stepping onto the stage to begin her audition."
a person who dissents from some established policy
"The old guard tried to silence her, but the contestant refused to accept their outdated rules on how the community should be governed."
A participant in a contest; specifically, a person who plays a game, as on a TV game show.
"The contestant nervously pressed the buzzer after hearing the final question on the game show."