ἐπεμβατήρ
From LSJ
Ποιητὴς, ὁπόταν ἐν τῷ τρίποδι τῆς Μούσης καθίζηται, τότε οὐκ ἔμφρων ἐστίν → Whenever a poet is seated on the Muses' tripod, he is not in his senses
English (LSJ)
ῆρος, ὁ, = ἐπεμβάτης (one mounted, horseman, one who walks on, one who walks in) ; v. ἐπαμβατήρ.
Greek (Liddell-Scott)
ἐπεμβᾰτήρ: ὁ, = ἐπεμβάτης· ἴδε ἐπαμβατήρ.