Definition of steady state in English:

steady state

noun

  • An unvarying condition in a physical process, especially as in the theory that the universe is eternal and maintained by constant creation of matter.

    • ‘The result for Milne's cosmology was a stationary universe with an infinite past age which, of course, acted as a precursor to the steady-state theory.’
    • ‘Earth science teachers could show why the steady-state theory of the universe lost out to the Big Bang’

The steady state theory postulates that the universe maintains a constant average density, with more matter continuously created to fill the void left by galaxies that are receding from one another. The theory has now largely been abandoned in favour of the Big Bang theory and an evolving universe