noun
Loanword from English; used to describe someone who works diligently and puts in a lot of effort. Often carries a positive or admiring tone.
彼は本当にハードワーカーで、毎日遅くまで働いている。
He is a real hard worker, staying late every day.
ハードワーカーな社員がプロジェクトを成功に導いた。
The hard-working employees led the project to success.
Borrowed from English 'hard worker'. The exact date of borrowing is uncertain, but it became common in Japanese business contexts in the late 20th century.