Definition of fuller's earth
: an earthy substance that consists chiefly of clay mineral but lacks plasticity and that is used as an adsorbent, a filter medium, and a carrier for catalysts
Origin and Etymology of fuller's earth
1fuller; from its earlier use as fulling agent
First Known Use: 15th century
Seen and Heard
What made you want to look up fuller's earth? Please tell us where you read or heard it (including the quote, if possible).