The point, with coordinates critical solution temperatures and critical composition, on a temperature-composition phase diagram at which the distinction between co-existent phases vanishes. In solid-solid, solid-liquid and liquid-liquid systems both upper and lower critical solution temperatures and corresponding critical solution compositions can occur. Synonymous with consolute point.
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 580 (https://doi.org/10.1351/pac199466030577)