αὐτὸν κέκρουκας τὸν βατῆρα τοῦ λόγου → you have struck the very threshold of the argument, you have struck the most important and chiefmost point
ἀκροβελής (-οῦς), -ές (Α)αυτός που έχει μυτερό άκρο.[ΕΤΥΜΟΛΟΓΙΑ < ἀκρο- (Ι) + -βελής < βέλος.