一鸣惊人
Meaning
To astonish everyone with a first success after a period of quiet preparation.
In a sentence
She said little for years, then 一鸣惊人 and won the national prize.
Usage note
Implies prior obscurity — the surprise is part of the meaning.
Where you see it in Brain Challenge
This idiom appears in the picture-idiom levels as a picture or number clue. When the clue shows numbers, the digits usually become the first characters of each half of the idiom — that is why so many chengyu start with 一, 三, 五, 七, 九 or 十.