Definition of mysterium in English:

mysterium

noun

Astronomy
historical
  • A mysterious element; specifically a hypothetical substance to which a galactic radio emission at 1665 megahertz was formerly attributed, later identified as an exceptionally strong component of a set of four spectral lines emitted by hydroxyl radicals in interstellar space.

Origin

1960s. Either from myster- + -ium, or from classical Latin mystērium mystery.

Pronunciation

mysterium

/mɪˈstɪərɪəm/