1. A circular band or ring, especially one worn as an ornament on the arm or wrist.
Usage: archaic; literary
2. An astronomical instrument consisting of graduated metal rings used to measure celestial coordinates.
Usage: historical; astronomy

Examples

• The ancient Roman woman wore a golden armilla on her wrist.
• Medieval astronomers used an armilla to map the positions of stars.
• The armilla was a common form of jewelry among wealthy citizens in antiquity.
• The museum displayed a bronze armilla from the Renaissance period.
• Tycho Brahe employed a large armilla in his observatory to observe planetary motion.