n.
Pronunciation: ' p ə r- ˌ l ī t
Function: noun
Etymology: French, from perle pearl
Date: 1833
: volcanic glass that has a concentric shelly structure, appears as if composed of concretions, is usually grayish and sometimes spherulitic, and when expanded by heat forms a lightweight aggregate used especially in concrete and plaster and as a medium for potting plants
– per · lit · ic \ ˌ p ə r- ' li-tik \ adjective