What, another acronym?
CMB stands for Cosmic Microwave Background. It is also sometimes called the CBR, for Cosmic Background Radiation, although this is really a more general term that includes other cosmological backgrounds, eg infra-red, radio, x-ray, gravity-wave, neutrino. The CMB contains hugely more energy than any other cosmic radiation source, however, so it is the dominant component of the overall CBR spectrum. Other acronyms, such as CMBR, are also sometimes used!
