walk-on
US /ˈwɑːk.ɑːn/
UK /ˈwɑːk.ɑːn/

1.
2.
a person who joins a sports team without having been specially recruited or given a scholarship
:
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He made the basketball team as a walk-on.
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Many successful athletes started as walk-ons.
1.
denoting a small part in a play or film, with no speaking lines
:
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It was a simple walk-on appearance.
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The director often uses walk-on actors for crowd scenes.