Gray

1. An achromatic colour intermediate between black and white.
2. An animal or thing of grey colour, such as a horse, badger, or salmon.
3. An extraterrestrial humanoid with grayish skin, bulbous black eyes, and an enlarged head.
4. A penny with a tail on both sides, used for cheating.

1. To become gray.

   My hair is beginning to gray.

2. To cause to become gray.
3. To turn progressively older, alluding to graying of hair through aging (used in context of the population of a geographic region)

   the graying of America

4. To give a soft effect to (a photograph) by covering the negative while printing with a ground-glass plate.

1. Having a color somewhere between white and black, as the ash of an ember.
2. Dreary, gloomy.
3. Having an indistinct, disputed or uncertain quality.
4. Relating to older people.

   the gray dollar, i.e. the purchasing power of the elderly

noun

In the International System of Units, the derived unit of absorbed dose of radiation (radiation absorbed by a patient); one joule of energy absorbed per kilogram of the patient's mass. Symbol: Gy