un·heard-of \ˌ ̷ ̷ˈ ̷ ̷ˌ ̷ ̷\adjective Etymology:un- (I) + heard of, past participle form of the phrase hear of, from hear (I) + of : previously unknown : new, unprecedented < a first novel by an unheard-of writer > < amphibious operations … would soon by necessary on an unheard-of scale — J.P.Baxter b. 1893 >