What does cosmic microwave background radiation mean?
• COSMIC MICROWAVE BACKGROUND RADIATION (noun) The noun COSMIC MICROWAVE BACKGROUND RADIATION has 1 sense: 1. (cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2.725 kelvin Familiarity information: COSMIC MICROWAVE BACKGROUND RADIATION used as a noun is very rare.