Coloring or decoration applied to pottery before glazing. (noun)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "underglaze" in a sentence
"Colored engobes can also be termed underglaze colors."
"Doucai is a porcelain that combines a blue-and-white underglaze with an overglaze decoration."
"Look at that unctuous underglaze in the palest, almost imperceptible blue, not too glassy, not too dull, and fired with absolute evenness and consistency."