WordReference Random House Unabridged Dictionary of American English © 2024stead′y state′ the′ory, [Astron.]- Astronomya theory in which the universe is assumed to have average properties that are constant in space and time so that new matter must be continuously and spontaneously created to maintain average densities as the universe expands. Also called stead′y state′ mod′el. Cf. big bang theory.
Collins Concise English Dictionary © HarperCollins Publishers::
steady-state theory n - a cosmological theory postulating that the universe exists throughout time in a steady state such that the average density of matter does not vary with distance or time. Matter is continuously created in the space left by the receding stars and galaxies of the expanding universe
Compare big-bang theory