Great age (3)
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "Prolonged period" , "Long period of time" , "thousand million years" , "Major division of geological time" , "Age, epoch" .)
I believe the answer is:
eon
(Other definitions for eon that I've seen before include "Prolonged period" , "Long period of time" , "thousand million years" , "Major division of geological time" , "Age, epoch" .)