dark matter

/D AA1 R K M AE0 T ER0/
noun
  1. 1

    Particles of matter that cannot be detected by their radiation but whose presence is inferred from gravitational effects.

  2. 2

    By restriction, particles that have mass, which does not readily interact with normal matter except through gravitational effects.

Source: https://en.wiktionary.org/wiki/dark%20matter