Devitrification \De*vit`ri*fi*ca"tion\, n.
The act or process of devitrifying, or the state of being
devitrified. Specifically, the conversion of molten glassy
matter into a stony mass by slow cooling, the result being
the formation of crystallites, microbites, etc., in the
glassy base, which are then called devitrification products.
[1913 Webster]