The Greek verb akmazō means to be at one's prime, to be ripe, or to reach full maturity. In Revelation 14:18, it describes grapes that are "ripe" for the great harvest of God's judgment.
Revelation 14:18 commands the angel with the sharp sickle: "Take your sharp sickle and gather the clusters of grapes from the earth's vine, because its grapes are ripe." This harvest imagery — drawn from Joel 3:13 — portrays the ripeness of human sin reaching the fullness of divine judgment. As God's people are being gathered into His kingdom (the grain harvest, v. 14–16), the wicked reach the full maturity of their rebellion. God's patience is real, but it has an end.