gray¹ / grā/ (Brit. grey) • adj. 1. of a color intermediate between black and white, as of ashes or an overcast sky: gray flannel trousers. ∎  (of hair) turning gray or white with age: a gray beard. ∎  (of a person) having gray hair: a gray, fatherly gentleman. ∎ inf. relating to old people, esp. when seen as an oppressed group: gray power. ∎  (of the weather) cloudy and dull; without sun: a cold, gray November day. ∎  (of a person's face) pale, as through tiredness, age, or illness: a few people, their faces gray and bitter.2. dull and nondescript; without interest or character: gray, faceless men the gray daily routine.3. (of financial or trading activity) not accounted for in official statistics: the gray economy.• n. 1. gray color or pigment: dirty intermediate tones of gray. ∎  gray clothes or material: the gentleman in gray. ∎  gray hair: he sighed at the amount of gray at his temple. ∎  (usu. Gray) the Confederate army in the Civil War, or a member of that army.2. a gray thing or animal, in particular a gray or white horse.• v. [intr.] (esp. of hair) become gray with age: he had put on weight and grayed somewhat | [as adj.] (graying) a man of about fifty with graying hair. ∎  (of a person or group) become older; age: [as adj.] (graying) a graying workforce. PHRASAL VERBS: gray something out display a menu option in a light font to indicate that it is not available: [usually passive] all the property fields on the Shortcut tab are either missing or grayed out.DERIVATIVES: gray·ish adj.gray·ly adv.gray·ness n.gray² (abbr.: Gy) • n. Physics the SI unit of the absorbed dose of ionizing radiation, corresponding to one joule per kilogram.

gray Symbol Gy. The derived SI unit of absorbed dose of ionizing radiation (see radiation units). It is named after the British radiobiologist L. H. Gray (1905–65).

gray(Gy) The SI unit of absorbed radiation dose, being an energy of 1 joule imparted by ionizing radiation to 1 kilogram of matter. It is named after the British radiologist L. H. Gray (1905–65).

gray (gray) n. the SI unit of absorbed dose of ionizing radiation, being the absorbed dose when the energy per unit mass imparted to matter by ionizing radiation is 1 joule per kilogram. It has replaced the rad. Symbol: Gy.

Gray (Gy) The SI unit for ionizing radiation (= 100 rad), equivalent to 1 J/kg.