\Tes*tu"do\, n.; pl. {Testudines}. [L., from testa the
shell of shellfish, or of testaceous animals.]
1. (Zo["o]l.) 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 Gr[ae]ca}) and the gopher of the
   Southern United States.
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.
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.