Argillaceous \Ar`gil*la"ceous\, a. [L. argillaceus, fr. argilla.]

Of the nature of clay; consisting of, or containing, argil or clay; clayey.

Argillaceous sandstone (Geol.), a sandstone containing much clay.

Argillaceous iron ore, the clay ironstone.

Argillaceous schist or state. See Argillite.

Source: Webster's Revised Unabridged Dictionary (1913)