σιγμός
From LSJ
καί τιν᾿ ὀίω αἵματί τ' ἐγκεφάλῳ τε παλαξέμεν ἄσπετον οὖδας ἀνδρῶν μνηστήρων, οἵ τοι βίοτον κατέδουσιν → and I think some one of the suitors that devour your property shall bespatter the vast earth with his blood and brains
English (LSJ)
ὁ, (σίζω)
A hissing, as of tortoises, Arist.HA536a7; as a signal, Plu.2.593b; in Magic, Plot.2.9.14; in Gramm., of sibilants, D.T.631.18, Phld.Po.Herc.994.33, S.E.M.1.102.
German (Pape)
[Seite 878] ὁ, das Zischen, Arist. H. A. 4, 9; der Zischlaut, S. Emp. adv. gramm. 102; auch σισμός, Sp.