“昙花一现的人或物”可以用英语表达为 “a flash in the pan” 或 “someone/something that is short-lived or ephemeral”。
1、 “a flash in the pan”：
这是一个常用的英语习语，形象地描述了某人或某物突然出现但很快又消失不见，就像昙花开放后迅速凋谢一样。
例如：He was a flash in the pan in the music industry, achieving quick fame but then disappearing from the scene.（他在音乐界只是昙花一现，迅速成名后又从舞台上消失了。）
2、 “someone/something that is short-lived or ephemeral”：
这种表达方式更为直接和具体，明确指出了某人或某物的短暂性。
例如：The popularity of that viral video was short-lived; it was just a flash in the pan.（那个病毒视频的流行是短暂的，只是昙花一现。）
或者：Her career as a model was ephemeral, lasting only a few years.（她作为模特的职业生涯是短暂的，只持续了几年。）