μήκυνσις
From LSJ
Ἄξιόν ἐστι τὸ ἀρνίον τὸ ἐσφαγμένον λαβεῖν τὴν δύναμιν καὶ τὸν πλοῦτον καὶ σοφίαν καὶ ἰσχὺν καὶ τιμὴν καὶ δόξαν καὶ εὐλογίαν → Worthy is the Lamb that was slain to receive power, and riches, and wisdom, and strength, and honour, and glory, and blessing
English (LSJ)
-εως, ἡ, lengthening, in prosody, Sch.D.T.p.49 H.
Greek (Liddell-Scott)
μήκυνσις: -εως, ἡ, τὸ μηκύνειν, ἐν προσῳδίᾳ, Α. Β. 822.