na-adjective, noun
Describes a state of intense, often single-minded effort or excitement, typically in the phrase 躍起になる. Can be positive (eager) or negative (desperate, worked up).
彼は試験に合格しようと躍起になっている。
He is desperate to pass the exam.
社員たちは新製品の開発に躍
The employees are eagerly working on the development of the new product.
The kanji 躍 (leap, dance) and 起 (rise, get up) combine to suggest a state of being roused to action, figuratively 'leaping up' in eagerness or desperation. The exact historical derivation is uncertain.