n. In Roman antiquity, a cuirass or corselet.n. In the middle ages, a military garment consisting of a loose jacket of leather upon which rings or small plates of iron were sewed; also, a coat of fence of any kind.n. In zoology, a case or covering likened to a coat of mail.n. An old name for a paste or lute with which vessels were coated in order to protect them when very strongly heated.n. In botany: Same as testa, 2.n. The silicious covering of the frustules of diatoms.