na-adjective, noun
hating to lose; competitive; unyielding
Describes a person who strongly dislikes losing and is determined to win; often used as a personality trait. Can be used as a noun or na-adjective.
See also: 負けず嫌い
彼は負け嫌いで、どんなゲームでも本気で勝ちにいく。
He hates to lose and goes all out to win in any game.
負け嫌
Because I have a competitive nature, I don't give up easily.
Synonymous; 負けず嫌い is slightly more common and literally means 'disliking not losing,' but both are used interchangeably for 'hating to lose.'
Compound of 負け (make, 'losing') + 嫌い (kirai, 'dislike').