blackbody
noun
black·body ˈblak-ˈbä-dē 
: an ideal body or surface that completely absorbs all radiant energy falling upon it with no reflection and that radiates at all frequencies with a spectral energy distribution dependent on its absolute temperature
Example Sentences
Recent Examples on the Web Moreover, this radiation should have the spectrum of a perfect blackbody, with only tiny imperfections at the ~0.01% level or less. 
Ethan Siegel, Forbes, 6 May 2021 But more sensitive measurements should undoubtedly reveal small deviations from the blackbody curve that COBE measured. Quanta Magazine, 30 June 2015 That would have shifted the CMB’s spectrum away from a blackbody. Quanta Magazine, 30 June 2015 That’s important, said John Mather, an astrophysicist at NASA Goddard who won a Nobel Prize in 2006 for measuring the CMB’s blackbody spectrum with COBE. Quanta Magazine, 30 June 2015 Two of the assumptions used to obtain the rules of blackbody radiation provide loopholes. Chris Lee, Ars Technica, 11 Sep. 2018
Ethan Siegel, Forbes, 6 May 2021 But more sensitive measurements should undoubtedly reveal small deviations from the blackbody curve that COBE measured. Quanta Magazine, 30 June 2015 That would have shifted the CMB’s spectrum away from a blackbody. Quanta Magazine, 30 June 2015 That’s important, said John Mather, an astrophysicist at NASA Goddard who won a Nobel Prize in 2006 for measuring the CMB’s blackbody spectrum with COBE. Quanta Magazine, 30 June 2015 Two of the assumptions used to obtain the rules of blackbody radiation provide loopholes. Chris Lee, Ars Technica, 11 Sep. 2018 Word History
First Known Use
1712, in the meaning defined above