\In`fu*so"ri*al\, a. (Zo["o]l.)
Belonging to the Infusoria; composed of, or containing,
Infusoria; as, infusorial earth.
{Infusorial earth} (Geol.), a deposit of fine, usually white,
   siliceous material, composed mainly of the shells of the
   microscopic plants called diatoms. It is used in polishing
   powder, and in the manufacture of dynamite.