realgar noun.
[rɪ'algǝ] LME.[medieval Latin from Spanish rejalgar from Arab. rahj al-ġār arsenic, lit. 'powder of the cave', from rahj powder + AL-2 + ġār cave.]A red monoclinic sulphide of arsenic that is an important source of that element, and was formerly used as a pigment and in fireworks. Also called
red arsenic,
red orpiment.
[TahlilGaran] English Dictionary ▲