Wäck'e or Wäck'y, n.

(Synop., § 130), n. [Ger. wacke, grau-wacke, M. H. Ger. wacke, O. H. Ger. waggo, a kind of stone, a flint, a pebble.] (Geol.) A rock nearly allied to basalt, of which it may be regarded as a more soft and earthy variety. Its color is a greenish-gray, brown, or black. It is opaque, yields easily to the knife, and has often a greasy feel. Lyell.