1. at the furthest point , and so either topmost = Lat. summus, or outermost = Lat. extremus:

2. highest, topmost , ἐν ἄκρηι πόλει = ἐν ἀκροπόλει, (Iliad by Homer); μέλαν ὕδωρ ἄκρον at its surface , (Iliad by Homer), etc.

3. outermost , ἄκρη χείρ, ἄκροι πόδες, ἄκρος ὦμος the end of the hand, ends of the feet, tip of the shoulder, (Iliad by Homer); ἐπ᾽ ἄκρων [ δακτύλων] on tiptoe , (Sophocles Tragicus); ἄκροισι λαίφους κρασπέδοις with the outermost edges of the sail, i. e. under close-reefed sails, (Euripides)

4. of Time, it denotes completeness , ἄκραι σὺν ἑσπέραι when eve was fully come , (Pindar); ἄκρας νυκτός at dead of night, (Sophocles Tragicus)

5. of Degree, the highest in its kind, exceeding good, consummate, excellent : of persons, (Herdotus Historicus), etc.; ἄκρος μάντις (Sophocles Tragicus):—;often with an accusative modi added, ψυχὴν οὐκ ἄκρος not strong in mind, (Herdotus Historicus); ἄκροι τὰ πολέμια, skilful in war, (Herdotus Historicus), etc.; also with genitive modi, οἱ ἄκροι τῆς ποιήσεως (Plato Philosophus); also, ἄκρος εἰς or περί τι (Plato Philosophus)

6. as Substantive, see. ἄκρα, ἄκρον.

7. neuter as adverb on the top or surface , just , ἄκρον ἐπὶ ῥηγμῖνος on the very edge of the surf, il.

8. exceedingly , (Theocritus Poeta Bucolicus)

9. utterly, completely , (Plato Philosophus) (ML)

highest; extreme; the top; extremity