double negative
noun [ C ] language uk/ˌdʌb.əl ˈneɡ.ə.tɪv/ us/ˌdʌb.əl ˈneɡ.ə.t̬ɪv/
双重否定
the use of two negatives (= words that mean "no") in the same phrase or sentence
The phrase "a not unfamiliar situation" is an example of a double negative. 短语“一种并非不熟悉的情况”就是一个双重否定的例子。