The reversible transition, on cooling, of a liquid to a mixture of a second liquid and a solid: \[\text{liquid}_{1}\rightleftarrows \text{liquid}_{2}+\text{solid}\]
Source:
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 586 (https://doi.org/10.1351/pac199466030577)