ἀκύρωσις
From LSJ
καὶ λέγων ὅτι Πεπλήρωται ὁ καιρὸς καὶ ἤγγικεν ἡ βασιλεία τοῦ θεοῦ· μετανοεῖτε καὶ πιστεύετε ἐν τῷ εὐαγγελίῳ → declaring “The time has been accomplished and the kingdom of God is near: start repenting and believing in the gospel!” (Μark 1:15)
Greek (Liddell-Scott)
ἀκύρωσις: -εως, ἡ, ἀθέτησις, Διον. Ἁλ. 8, 21.