Dark matter is material that is believed to form a large part of the universe, but which has never been seen.
dark matter in British English
noun
astronomy
matter known to make up perhaps 90% of the mass of the universe, but not detectable by its absorption or emission of electromagnetic radiation
dark matter in American English
invisible matter whose existence is postulated by astrophysicists to account for the large amount of observed gravitation that cannot be accounted for by visible matter
Examples of 'dark matter' in a sentence
dark matter
The Australian instruments will research the composition of the universe, including dark matter and dark energy.
Times, Sunday Times (2012)
Some 25 per cent is thought to be dark matter and another 70 per cent to be still more mysterious dark energy.
Times, Sunday Times (2009)
Q What's the dark matter causing the universe to expand?