testudo

‖n.; pl. Testudines [ L., from testa the shell of shellfish, or of testaceous animals. ] 1. (Zool.) A genus of tortoises which formerly included a large number of diverse forms, but is now restricted to certain terrestrial species, such as the European land tortoise (Testudo Graeca) and the gopher of the Southern United States. [ 1913 Webster ]

2. (Rom. Antiq.) A cover or screen which a body of troops formed with their shields or targets, by holding them over their heads when standing close to each other. This cover resembled the back of a tortoise, and served to shelter the men from darts, stones, and other missiles. A similar defense was sometimes formed of boards, and moved on wheels. [ 1913 Webster ]

3. (Mus.) A kind of musical instrument. a species of lyre; -- so called in allusion to the lyre of Mercury, fabled to have been made of the shell of a tortoise. [ 1913 Webster ]