The name Admatha means “a cloud of death; a mortal vapor”.
Smith's Bible Dictionary 1863
(given by the highest), one of the seven princes of Persia. (Esther 1:14)
International Standard Bible Encyclopedia 1915
ad'-ma-tha, ad-ma'-tha ('adhmatha'): One of "the seven princes of Persia and Media, who saw the king's face, and sat first in the kingdom" (Es 1:14); compare 2Ki 25:19; Ezr 7:14. The Septuagint gives only three names.