三长两短
Meaning
An unexpected misfortune or accident. Almost always used in the phrase 有个三长两短 ("if anything happens to him").
In a sentence
Take care on the road — I do not want to hear of any 三长两短.
Usage note
A euphemism. It softens the mention of death or serious injury rather than naming it.
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.