ἀδελφιδοῦς
From LSJ
Τὸ νικᾶν αὐτὸν αὑτὸν πασῶν νικῶν πρώτη τε καὶ ἀρίστη. Τὸ δὲ ἡττᾶσθαι αὐτὸν ὑφ' ἑαυτοῦ πάντων αἴσχιστόν τε ἅμα καὶ κάκιστον. → Τo conquer yourself is the first and best victory of all, while to be conquered by yourself is of all the most shameful as well as evil
German (Pape)
[Seite 32] ὁ, Neffe, Bruder- od. Schwestersohn, 'Thuc. u. Folgde.
French (Bailly abrégé)
v. ἀδελφιδέος.
Russian (Dvoretsky)
ἀδελφιδοῦς: стяж. к ἀδελφιδεός.
Lexicon Thucydideum
filius fratris vel sororis, son of a brother or sister, 2.101.6. 4.101.5.