LSJ
Dor. ματραδελφεός, Pi. P. 8.35; ὁ and ἡ : — mother΄s brother or sister, uncle or aunt, BGU 1158.3, Poll. 3.22.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
ὁ, u. ἡ, Mutterbruder, Mutterschwester, Oheim, Base, Poll. 3.22.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)