Meaning of JET in English

n. 1 a a hard black variety of lignite capable of being carved and highly polished. b (attrib.) made of this. 2 (in full jet-black) a deep glossy black colour.

[ ME f. AF geet, OF jaiet f. L gagates f. Gk gagates f. Gagai in Asia Minor ]

Concise Oxford English dictionary.      Краткий оксфордский словарь английского языка.