1. small circles whose centers move around the circumference of larger circles, used in ancient astronomy to explain planetary motion
Usage: astronomy; historical
2. complex systems or theories with many intricate parts added to explain observed phenomena
Usage: figurative

Examples

• Ptolemy used epicycles to account for the apparent backward motion of planets.
• The ancient model required dozens of epicycles to match observations.
• Copernicus simplified astronomy by eliminating most epicycles.
• The theory became burdened with epicycles to explain every exception.
• Scientists avoided adding epicycles to their elegant model.
• The explanation grew into a system of epicycles upon epicycles.