Source : Webster's Revised Unabridged Dictionary (1913)

Smectite \Smec"tite\, n. [G. smectit, fr. Gr. ????? a kind of
   fuller's earth, fr. ????? to wipe off.] (Min.)
   A hydrous silicate of alumina, of a greenish color, which, in
   certain states of humidity, appears transparent and almost
   gelatinous.