ἔμβολος
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)
ὁ, or ἔμβολον, τό,
A anything pointed so as to be easily thrust in, a peg, stopper, CIG2855.27, Poll.1.145; linch-pin (masc.), Pherecyd. 37(a) J.: Com. for πέος, Ar.Fr.317 (masc.). 2 τῆς χώρης ἔμβολον tongue of land, Hdt.4.53; Ἀσίας ἔμβολον prob. the headland of Κυμὸς σῆμα in Caria, Pi.O.7.19 (ἔμβολος Ἀσίας ἡ Λυκία Sch.ad loc.). 3 brazen beak, ram, masc. in Hdt.1.166, Tab.Heracl.1.166,182; neut. in AP6.236 (Phil.), Paus 6.20.10; gender doubtful in Pi.P.4.191, Th.7.36. b οἱ ἔ.,= Lat. rostra, tribune of the Roman forum, Plb.6.53.1, Plu.Cat.Mi.44. 4 wedge-shaped order of battle, neut. in X.HG7.5.22, Plb.1.26.16; of a march-formation, Ael.Tact.37.6, Arr.Tact.29.5; τὸ τρίγωνον σχῆμα ἔμβολόν τε καὶ σφηνοειδὲς ὀνομάζεται Ascl.Tact.7.6; ἡ ὅλη [τάξις] λέγεται ἔμβολος ib.11.5. b ἔμβολον, τό, half a ῥόμβος (q. v.) of cavalry, ib.7.3, Ael.Tact. 19.5. 5 bolt, bar, E.Ph.114 (neut., anap.). 6 λάϊνα κίοσιν ἔμβολα prob.= τὰ κίοσιν ἐμβεβλημένα, architrave, Id.Ba.591 (lyr.). 7 graft, Gp 10.77.4. 8 portico, IG11 (2).161 D 118 (Delos, iii B. C.), Ephes.3 No.8, CIG4662b (Gerasa), interpol. in Hld.2.26; ἔ. τῆς κρατίστης βουλῆς BCH11.474 (Lydia). 9 ἔμβολος· εἶδος θηρίου ἐν λαχάνοις, Hsch.
