adjective

1. tending to keep its form rather than to flow or spread out like a liquid or gas; relatively firm or compact
2. filled with matter throughout; not hollow
3. 1. having the three dimensions of length, breadth, and thickness prisms and other solid figures
   2. dealing with bodies or figures in three dimensions
4. 1. firm, strong, and dependable a solid structure
   2. substantial, sound, and reliable solid reasoning
   3. sturdy or vigorous a solid build, a solid punch
5. serious; not superficial or trivial solid scholarship
6. complete, thoroughgoing, or genuine solid satisfaction
7. 1. having no breaks or divisions a solid line of fortifications
   2. written or printed without a hyphen a solid compound
8. characterized by no pauses or interruptions to talk for a solid hour
9. 1. of one or the same color, material, or consistency throughout a solid walnut table
   2. consisting of one unalloyed metal throughout; also, containing no more alloy than is necessary to insure hardness: said of gold, etc.
10. ☆ characterized by or showing complete unity; unanimous a solid vote
11. thick or dense in appearance or texture a solid fog
12. firm or dependable a solid friendship
13. ☆ Informal having a firmly favorable or good relationship to be in solid with someone
14. Informal healthful and filling a solid meal
15. ☆ Slang very good; excellent a solid dance band
16. Printing set without spaces between the lines of type

Etymology: ME solide < MFr < L solidus < sollus, whole: see solemn

noun

1. a substance that is solid, not a liquid or gas
2. an object or figure having or represented as having length, breadth, and thickness