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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

He struts around shirtless and shoeless; his wife and homeschooled sons, Stryker and Rad, pad about barefooted as well.

From Salon • Jun. 1, 2025

Since then, he has built five more, with names including Dalek Rad, Dalek Bert and Dalek Blisteron.

From BBC • May 30, 2025

“There needs to be a systematic retraining,” said Abdul Nasser Rad, managing director of research and data at Campaign Zero, a nonprofit group that focuses on criminal justice reform and helped draft the California law.

From Los Angeles Times • Oct. 12, 2023

The study was led by Arash Modaresi Rad, a doctoral student at Boise State University, and his advisor, Mojtaba Sadegh, an associate professor of civil engineering.

From Science Daily • Sep. 20, 2023

The discovery of carbon-14 was the high water mark of Kamen s career in the Rad Lab; its publication was the beginning of his painful journey out of Lawrence’s good graces.

From "Big Science" by Michael Hiltzik

Related Words

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