τριπτέον
From LSJ
Δελφῖνα νήχεσθαι διδάσκεις: ἐπὶ τῶν ἐν ἐκείνοις τινὰ παιδοτριβούντων, ἐν οἷς ἤσκηται → Teaching dolphins to swim: is applied to those who are teaching something among people who are already well versed in it
English (LSJ)
(τρίβω) A one must rub or grind, Gal.6.229, Gp.5.51.2.
Greek (Liddell-Scott)
τριπτέον: ῥημ. ἐπίθετ. τοῦ τρίβω, δεῖ τρίβειν, Γεωπον. 5. 51, 17.
