tes·ta·ceous \(ˈ) ̷ ̷| ̷ ̷shəs\adjective Etymology: Latin testaceus consisting of bricks, covered with a shell, from testa piece of burned clay, brick, shell + -aceus -aceous 1.obsolete: of, relating to, or made of earthenware 2. a.: having a shell < a testaceous protozoan > b.: consisting of shell or calcareous material < stone … of a pale reddish brick color, and a testaceous composition — Mark Van Doren > 3.: of any of the several light colors of bricks, averaging the color pheasant