ἢ λέγε τι σιγῆς κρεῖττον ἢ σιγὴν ἔχε → either say something better than silence or keep silence (Menander)
adj.
Of a military position, strong: P. and V. ὀχυρός; see strong.
Of an argument: P. ἀνέλεγκτος.