solid state (Adjective) — Characteristic of or relating to the physical properties of solid materials especially electromagnetic or thermodynamic or structural properties of crystalline solids.
solid state (Adjective) — (electronics) consisting of semiconductor materials and components and related devices.
solid state (Noun) — The state in which a substance has no tendency to flow under moderate stress; resists forces (such as compression) that tend to deform it; and retains a definite size and shape.