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P. and V. δύσμαχος, ἀνίκητος, Ar. and P. ἄμαχος (Plato), P. δυσπολέμητος, V. δυσπάλαιστος, ἀπρόσμαχος, ἀδήριτος.
impossible to deal with: P. and V. ἄπορος, ἀμήχανος (rare P.).
obstinate: see obstinate.