noun
loss by default; default loss
Used in sports, games, and competitions when a player or team loses because they did not show up, were disqualified, or otherwise failed to compete. Often contrasted with 不戦勝 (win by default).
See also: 不戦勝
相手が試合に来なかったので、不戦敗になった。
The opponent didn't show up for the match, so it became a loss by default.
棄権すると不戦敗とみなされる。
If you withdraw, it is considered a default loss.