Try Our Apps


90s Slang You Should Know


[ground-mas] /ˈgraʊndˌmæs/
the crystalline, granular, or glassy base or matrix of a porphyritic or other igneous rock, in which the more prominent crystals are embedded.
Origin of groundmass
First recorded in 1875-80; ground1 + mass Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
Cite This Source
Examples from the Web for groundmass
Historical Examples
  • These lavas have groundmass textures that vary from almost holo-crystalline to glassy.

    Mount Rainier Various
  • In a basal flow in Moraine Park, the slaggy and compact phases show differences in phenocrysts as well as in groundmass.

    Mount Rainier Various
  • Pyroxene, quartz and augite form the groundmass, as seen in section.

    The Long Labrador Trail Dillon Wallace
British Dictionary definitions for groundmass


the matrix of igneous rocks, such as porphyry, in which larger crystals (phenocrysts) are embedded
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Cite This Source

Word of the Day

Difficulty index for groundmass

Many English speakers likely know this word

Word Value for groundmass

Scrabble Words With Friends

Nearby words for groundmass