The definition of agone is an archaic (no longer really used) version of the word ago meaning past or bygone.(adjective)
An example of the word agone is when something happened five days prior.
See agone in Webster's New World College Dictionary
Origin: ME agon, ago
See agone in American Heritage Dictionary 4
adverb & adj.
Origin: Middle English agon
Origin: , past participle of agon, to go away; see ago.