Abbott-Smith Manual Greek Lexicon
ἄκρος (G206)
6 ἄκρος , -α, -ον [in LXX for קֶצַח , בֹּהֶן , etc.;] highest , extreme ; as subst., τὸ ἄ. , the top , extremity : Mk 13:27 , Lk 16:24 , He 11:21 ; pl. (cf. MM, VGT , s.v.), Mt 24:31 .†
G. Abbott-Smith, A Manual Greek Lexicon of the New Testament (1922) — public domain