a thievish nature; a base tendency to take what belongs to others or behave dishonorably.
彼は小さなことで人の物を取ってしまう、泥棒根性が抜けない。
He can't shake his thievish habit of taking other people's things over trivial matters.
泥棒根性で人の働きを横取りするような真似はやめなさい。
Stop behaving like a thief and taking credit for others' work.
子供に泥棒根性を育てないため、物を借りたら返すことを教えた。
To prevent a thievish attitude, I taught the child to return things they borrow.