testudo

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A Roman siege device consisting of a movable screen protecting the besiegers' approach to a wall.
2. n. A cover formed by the overlapping shields of besiegers and held over their heads.

Century Dictionary and Cyclopedia

1. n. Among the ancient Romans, a defensive cover or screen which a body of troops formed by overlapping above their heads their oblong shields when in close array. This cover somewhat resembled the back of a tortoise, and served to shelter the men from missiles thrown from above. The name was also given to a structure movable on wheels or rollers for protecting sappers. Formerly also called snail.
2. n. A shelter similar in shape and design to the above, employed as a defense by miners and others when working in ground or rock which is liable to cave in.
3. n. In medicine, an encysted tumor, which has been supposed to resemble the shell of a turtle. Also called talpa.
4. n. [capitalized] In herpetology, the typical genus of Testudinidæ, of widely varying limits with different authors, and much confused with Cistudo. It now contains such tortoises as T. græca of Europe and some others. See cut on following page, also that under Testudinata.
5. n. In anatomy, the fornix: more fully called testudo cerebri. See cerebrum.
6. n. In ancient music, a species of lyre: so called in allusion to the lyre of Mercury, fabled to have been made of the shell of the sea-tortoise. The name was also extended in medieval music to the lute.

GNU Webster's 1913

1. n. (Zoöl.) 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 Græca) and the gopher of the Southern United States.
2. n. (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. n. (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.

WordNet 3.0

1. n. a movable protective covering that provided protection from above; used by Roman troops when approaching the walls of a besieged fortification
2. n. type genus of the Testudinidae