(adj) without warning or announcement; ; - M.A.D.Howe, Syn. unheralded, unpredicted, Example:they arrived unannounced; a totally unheralded telegram that his daughter...died last night
[天有不测风云 / 天有不測風雲, tiān yǒu bù cè fēng yúnㄊㄧㄢ ㄧㄡˇ ㄅㄨˋ ㄘㄜˋ ㄈㄥ ㄩㄣˊ] fortune as unpredictable as the weather (成语 saw); sth unexpected may happen at any moment#58033
[天有不测风云,人有旦夕祸福 / 天有不測風雲,人有旦夕禍福, tiān yǒu bù cè fēng yún, rén yǒu dàn xī huò fúㄊㄧㄢ ㄧㄡˇ ㄅㄨˋ ㄘㄜˋ ㄈㄥ ㄩㄣˊ, ㄖㄣˊ ㄧㄡˇ ㄉㄢˋ ㄒㄧ ㄏㄨㄛˋ ㄈㄨˊ] fortune as unpredictable as the weather, every day may bring fortune or calamity (成语 saw); sth unexpected may happen at any moment