aeon \aeon\, AEon \[AE]"on\, n. 1. A period of immeasurable duration. See {Eon}. [1913 Webster] 2. (Gnosticism) a divine power or nature emanating from the Supreme Being and playing various roles in the operation of the universe. Syn: eon [WordNet 1.5] 3. the longest division of geological time; two or more eras. Syn: eon [WordNet 1.5]