adverb
in one leap; skipping intermediate steps; directly
Describes advancing to a higher level or stage without going through the usual intermediate steps. Often used with verbs like 進む, 上がる, or なる.
彼は平社員から一足飛びに部長になった。
He jumped straight from regular employee to department head.
初心者が一足飛びに上級者向けのコースを受けるのは難しい。
It's hard for a beginner to jump straight into an advanced course.
Compound of 一足 (one step) and 飛び (jumping), literally 'in one leap'. The adverbial form に indicates manner.