Tes-tū'do, n.

n. [Lat., from testa, the shell of shell-fish, or of testaceous animals; Fr. testudo, It. testudine, testuggine.] [See Illust. of Tortoise.]

1. (Zool.) A genus of animals, in the Linnean system, now represented by the genus Chelonia; the tortoise.
2. Among the ancient Romans, 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. (Med.) An encysted tumor, so called as supposed to resemble a tortoise in form;—called also talpa. Dunglison.
4. (Mus.) A 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.