undefeated
adj. B2 Upper Intermediate US //ˌəndɪˈfitɪd// UK //ˌʌndɪfˈiːtɪd// un·de·feat·ed
adj. having never lost a game, fight, or competition. You use this to describe a team or person with a perfect record.
adj. having suffered no defeats in a series of contests or competitions. Often used to describe a sports team's season or a professional fighter's career record.
The local football team remains undefeated this season.
After twelve professional matches, the boxer is still undefeated and holds the championship belt.
Maintaining an undefeated record throughout a long tournament requires not only physical stamina but also the mental resilience to perform under the pressure of high expectations.
From un- + defeated.
Usage
Typically used as a predicative adjective following a linking verb like 'remain' or 'stay'.