Solid  —adj. (-der, -dest) 1 firm and stable in shape; not liquid or fluid. 2 of such material throughout, not hollow. 3 of the same substance throughout (solid silver). 4 sturdily built; not flimsy or slender. 5 a three-dimensional. B of solids (solid geometry). 6 a sound, reliable (solid arguments). B dependable (solid friend). 7 sound but unexciting (solid piece of work). 8 financially sound. 9 uninterrupted (four solid hours). 10 unanimous, undivided. 11 (of printing) without spaces. —n. 1 solid substance or body. 2 (in pl.) Solid food. 3 geom. Three-dimensional body or magnitude. —adv. Solidly (jammed solid).  solidly adv. Solidness n. [latin solidus]