what is a solid matter
View full size image. Solid is one of the three main states of matter, along with liquid and gas. Matter is the stuff of the universe, the atoms, molecules and ions that make up all physical substances. In a solid, these particles are packed closely together and are not free to move about within the substance.
Part of the IT standards and organizations glossary: A solid is a sample of matter that retains its shape and density when not confined. The adjective solid describes the state, or condition, of matter having this property.