ミリグレイMeanings1nounmilligrayphysicsA unit of absorbed radiation dose equal to one-thousandth of a gray (Gy). Used in physics and radiation measurement.See also: グレイこの地ち域いきの年ねん間かん放ほう射しゃ線せん量りょうは約やく2ミリグレイです。The annual radiation dose in this area is about 2 milligrays.