noun
junior middleweight
Boxing weight class between welterweight and middleweight, typically with a limit of 154 pounds (69.9 kg).
彼はジュニアミドル級のタイトルを防衛した。
He defended the junior middleweight title.
From English 'junior middleweight' with 級 (class/division) appended, forming a standard Japanese boxing weight class term.