diatomaceous earth

noun

1. a fine siliceous earth composed chiefly of the cell walls of diatoms: used in filtration, as an abrasive, etc.

noun

1. an unconsolidated form of diatomiteAlso called: kieselguhr

n.

1. A powder made of the desiccated shells of diatoms, used as a filtering agent, adsorbent, and abrasive in many chemical operations.