A process in a phase transition in which nuclei of a new phase are first formed, followed by the propagation of the new phase at a faster rate.
See: continuous precipitation, discontinuous precipitation, phase transition
Source:
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 587 (https://doi.org/10.1351/pac199466030577)