auto-open umbrella; push-button umbrella
An umbrella that opens automatically with the press of a button, often spring-loaded.
雨が急に降ってきたので、ジャンプ傘をさっと開いた。
It suddenly started raining, so I quickly opened my auto-open umbrella.
Compound of ジャンプ (jump, from English) and 傘 (umbrella), referring to the spring-loaded opening mechanism.