- 1: to change from a fluid to a solid state by or as if by cold
- 2: to make viscid or curdled : coagulate
- 3: to make rigid, fixed, or immobile
Congelation is the process by which something congeals, or thickens. This increase in viscosity can be achieved through a reduction in temperature or through chemical reactions. Sometimes the increase in viscosity is great enough to crystallize or solidify the substance in question.
In alchemy, congelation is one of the 12 vital processes for transformation to occur.