unawares
adverb uk/ˌʌn.əˈweəz/ us/ˌʌn.əˈwerz/
出其不意地，意外地，冷不防地
suddenly and unexpectedly without any warning
The overnight invasion took the military experts unawares. 一夜间突然入侵令军事专家们始料不及。
The government was obviously caught unawares by (= was not expecting) the criticism. 政府似乎对这突然发起的抨击猝不及防。