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• rad
  rad

  noun

  a unit of absorbed dose of radiation equal to 0.01 gray: not a standard SI unit, the rad is still used, especially in the U.S., but it is increasingly disfavored.
• rad.
  rad.

  abbreviation

  radical.

rad

¹ American  

[rad] / ræd /

noun

Physics.

1. a unit of absorbed dose of radiation equal to 0.01 gray: not a standard SI unit, the rad is still used, especially in the U.S., but it is increasingly disfavored.

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rad ² American  

[rad] / ræd /

noun

1. Informal. a radical, especially a person with extreme views on political and social issues.

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adjective

radder, raddest

1. Slang. excellent; wonderful; cool.

   a high speed, high energy, totally rad racing game.

rad ³ American  

[rad] / ræd /

abbreviation

Mathematics.

1. radian; radians.

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rad. ⁴ American  

abbreviation

Mathematics.

1. radical.

2. radix.

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rad ¹ British  

/ ræd /

noun

1. a former unit of absorbed ionizing radiation dose equivalent to an energy absorption per unit mass of 0.01 joule per kilogram of irradiated material. 1 rad is equivalent to 0.01 gray

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rad ² British  

symbol

1. radian

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rad. ³ British  

abbreviation

1. radical

2. radius

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rad Scientific  

/ răd /

1. A unit used to measure energy absorbed by a material from radiation. One rad is equal to 100 ergs per gram of material. Many scientists now measure this energy in grays rather than in rads.

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rad Cultural  

1. An acronym for r adiation a bsorbed d ose. A unit of energy absorbed from ionizing radiation.

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Etymology

Origin of rad¹

First recorded in 1915–20; r(adiation) a(bsorbed) d(ose)

Origin of rad²

First recorded in 1820–25 rad ² for 1; 1975–80 rad ² for 2; shortening of radical

Origin of rad³

First recorded in 1910–15; shortening

Example Sentences

Hahn: This woman had been working with Marvel and “Agatha,” and so she was kind of sent my way, and then I kept working with her, and she’s rad.

From Los Angeles Times • Jun. 5, 2025

“We believe in respect, kindness, and love. We are huge fans of other women-owned companies, LGBTQIA+ communities, and rad men’s companies too. None of that feels political to us,” she said.

From Slate • Jul. 23, 2024

I feel like I never imagined a year in my career where I would get to work more than I am not working, and that's happening, and that's pretty rad.

From Salon • Jun. 4, 2023

“The place is rad; there’s no place like this,” said Matt Collette, 48, who joined Kim’s Friends of Gardena Cinema volunteer group, which has continued to expand since October.

From Los Angeles Times • May 19, 2023

I’m not going to hop in unless there’s something really rad.

From "Free Lunch" by Rex Ogle

Related Words

• astonishing
• astounding
• awesome
• breathtaking
• fantastic
• incredible
• marvelous
• outrageous
• phenomenal
• remarkable
• spectacular
• superb
• terrific
• unbelievable