LSJ

κέντρον , to/, (κεντέω)
A. [select] any sharp point:
1. [select] horse-goad, [“ἵπποι] ἄνευ κέντροιο θέοντες” Il.23.387, cf. 430, Ar.Nu.1297, X.Cyr.7.1.29, etc.; “διπλοῖς κέντροισι” S.OT809; “ὄνειδος ἔτυψεν δίκαν διφρηλάτου μεσολαβεῖ κ.” A.Eu.157 (lyr.): post-Hom., ox-goad (Hom. βουπλήξ), used as an instrument of torture, Hdt.3.130; “κέντροις καὶ μάστιξιν” Pl.Lg.777a: prov., πρὸς κέντρα λακτίζειν (v. “λακτίζω” 2); “δεῖ . . κέντρου πολλάκις, οὕτω δὲ καὶ χαλινοῦ” Longin.2.2; as a symbol of sovereignty, “λαβὼν . . χερσὶν κέντρα κηδεύει πόλιν” S.Fr.683.
b. [select] metaph., goad, spur, incentive, Pi.Fr.124.4, A.Pr.691 (lyr.); ποῦ γὰρ τοσοῦτο κ. ὡς μητροκτονεῖν; Id.Eu.427; “κέντροις ἔρωτος” E.Hipp.39, cf.1303; “πόθου κ.” Pl.R.573a; “κέντρα καὶ ὠδῖνες” Id.Phdr.251e; “κ. ἐγερτικὸν θυμοῦ” Plu.Lyc.21; κέντρα πτολέμοιο, of the Argives, Orac. ap. Sch.Theoc.14.48; κ. ἐμοῦ desire for me, S.Ph.1039.
2. [select] metaph., in pl., tortures, pangs, Id.Tr.840 (lyr.): sg., “τὸ κ. τοῦ θανάτου ἡ ἁμαρτία” 1 Ep.Cor.15.56.
3. [select] point of a spear, Plb.6.22.4: pl., of the περόναι with which Oedipus pierced his eyes, S.OT1318.
4. [select] peg of a top, Pl.R. 436d.
5. [select] of animals,
a. [select] sting of bees and wasps, Ar.V.225, 407 (lyr.), al.; of scorpions, Arist.PA683a12 (so of the constellation Scorpio, Arat.505): hence, metaph., of malicious persons, “ἐς τοὺς ἔχοντας κέντρ᾽ ἀφιᾶσιν” E.Supp.242; “πορεύεται, ὥσπερ σκορπίος, ἠρκὼς τὸ κ.” D.25.52; of Pericles as an orator, “τὸ κ. ἐγκατέλειπε τοῖς ἀκροωμένοις” Eup.94.7; of Socrates, “ὥσπερ μέλιττα τὸ κ. ἐγκαταλιπών” Pl.Phd.91c; “οἷον ὀφθαλμῷ κ. ἐνθεῖσα” Philostr.Im.2.1; βλέμματος κ. Onomarch. ap. Philostr.VS2.18.
b. [select] spur of a cock, Gp.14.7.17.
c. [select] quill of the porcupine, Ael.NA12.26.
d. [select] = πόσθη, Sotad.1.
6. [select] stationary point of a pair of compasses, Vitr.3.1.3: generally, centre of a circle, Pl. Ti.54e, Arist.APr.41b15, al.; ἡ ἐκ τοῦ κ. (sc. εὐθεῖα) radius, Euc.Opt. 34; “ὥσπερ κύκλον κέντρῳ περιέγραψαν τὴν πόλιν” Plu.Rom.11; “τὸ κ. τᾶς σφαίρας” Ti.Locr.100e; “τὸ κ. τῆς γῆς” Ptol.Tetr.52; κ. βάρεος centre of gravity, Archim.Aequil.1Def.4: metaph., κ. καὶ διαστήματι περιγράφειν circumscribe, Plu.2.513c, 524f.
7. [select] pin, rivet, Paus.10.16.1; spur, tip, for fixing a machine in the ground, Apollod Poliorc. 144.1.
8. [select] ῥακτηρίοις κέντροισιν, of oars, S.Fr.802.
9. [select] Astron., cardinal point on the ecliptic, Ptol.Tetr.74, S.E.M.5.12, Vett.Val.50.18, etc.
10. [select] hard knot in stone, Thphr.HP5.2.3; flaw in crystals, Plin.HN37.28.

http://www.perseus.tufts.edu/hopper/morph?l=ke/ntra&la=greek&prior=pros&d=Perseus:text:1999.01.0009:card=325&i=1#lexicon