Supercritical carbon dioxide is a fluid state of #CO_2# at which both the temperature and the pressure exceed the critical point - the highest temperature and pressure at which the substance can exist as a vapor and liquid in equilibrium - of #31^@C# ( or 304.15K) and #73atm#.
If you look at #CO_2#'s phase diagram, this region corresponds to the upper-right portion of the diagram. When in a supercritical state, #CO_2# has both gas-like and liquid-like qualities - it acts as a supercritical fluid for which distinct gas and liquid phases do not exist.
Supercritical fluids can dissolve materials like a liquid and effuse through solids as a gas, and are often used as a substitute for organic solvents for industrial or laboratory processes. This dissolving ability can be apllied to extract, purify, recristallize, infuse, or fractionate various materials
By controlling its temperature and/or pressure, supercritical #CO_2# can be made to dissolve a wide range of materials.