noun
poor loser; sour grapes; unwillingness to admit defeat
Describes the attitude of someone who cannot accept losing gracefully and makes excuses or disparages the winner. Often used in the phrase 負け惜しみを言う.
彼は試合に負けた後、負け惜しみばかり言っていた。
After losing the match, he kept making sour-grapes remarks.
負け惜しみ
It's unbecoming to be a sore loser.