"Aeonian" is an adjective derived from the Greek word aion, meaning "age" or "eternity." It refers to something that is timeless, eternal, or lasting for an immeasurable length of time. Often used in a poetic or philosophical sense, "aeonian" conveys the idea of something that transcends the limits of time, enduring forever or for an exceedingly long period. It can be used to describe anything that has a sense of permanence or infinite duration, such as love, beauty, or wisdom.

The term is closely related to ideas of eternity and timelessness, often invoking a sense of grandeur and permanence beyond the transient nature of human life.