Physics,Astron. 1. (in relativity) a property of space near massive bodies in which their gravitational field causes light to travel along curved paths.
2. (in cosmology) a large-scale property of the universe that has an algebraic sign that depends upon whether the density of matter and radiation of the universe exceeds, equals, or is less than the critical density, leading, respectively, to a closed universe with a positive sign, a flat universe with value zero, or an open universe with a negative sign.