Final answer:
Frit is a fused or partially fused material that is ground to introduce a soluble or unstable ingredient into glazes or enamels.
Step-by-step explanation:
The fused or partially fused material that is ground to introduce a soluble or unstable ingredient into glazes or enamels is called frit. Frit is a glass material that is used in ceramics to provide color, opacity, or other desired properties to the glaze or enamel. It is made by melting and then cooling a mixture of various ingredients, including silica, alumina, and flux.