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