epicycle
Pronunciation:
/ˈɛpɪˌsaɪkəl/noun
Definitions
A small circle whose centre is on the circumference of a larger circle; in Ptolemaic astronomy it was seen as the basis of revolution of the "seven planets", given a fixed central Earth.
Any circle whose circumference rolls around that of another circle, thus creating a hypocycloid or epicycloid.
A ring of atoms joining parts of an already cyclic compound