- a hard, iridescent substance that forms the inner layer of certain mollusk shells, used for making buttons, beads, etc.; nacre.
- of or having the qualities of mother-of-pearl, as being iridescent or pearly: mother-of-pearl buttons.
- a hard iridescent substance, mostly calcium carbonate, that forms the inner layer of the shells of certain molluscs, such as the oyster. It is used to make buttons, inlay furniture, etc
