Lexical Definition

‎στῆθος‎ stēthos (stay'-thos) chest ^G:N-N
from ‎ἵστημι‎ (as standing prominently)

breast.

• the (entire external) bosom, i.e. chest

Abbott-Smith

στῆθος, -ους, τό [in LXX: Ex 28:23*, 26 (29, 30)* (לֵב), etc. ;]
the breast: Jo 13:25 21:10, Re 15:6; as a sign of penitence, τύπτειν (εἰς) τὸ σ., Lk 18:13 23:48,†

Abbott-Smith References

Liddell-Scott-Jones

στῆθος, εος, τό,

breast, of both sexes, being the front part of the θώραξ, divided into two μαστοί [Refs 8th c.BC+] in post-Homeric verse; found once in [Refs 8th c.BC+]; of animals, [Refs 5th c.BC+]; σ. φάσσης ἑψημένης [Refs 2nd c.AD+]: as the seat of the voice and breath, [Refs 8th c.BC+]; more frequently as the seat of the heart, [Refs 8th c.BC+]; chest, [Refs 5th c.BC+]; τὰ σ. breasts of a woman, [Refs 5th c.BC+]

__II metaphorically, the breast as the seat of feeling and thought, as we use heart, frequently in [Refs 8th c.BC+], but always in plural, θυμὸν ἐνὶ στήθεσσιν ὄρινε [Refs 8th c.BC+]; ἔχει κότον.. ἐν σ. ἑοῖσι[Refs 8th c.BC+]
__III ={στέρνον} [Refs]breastbone, [Refs 5th c.BC+]
__III.2 ball of the foot, [στῆθος 4th c.BC: Aristoteles Philosophus “Historia Animalium” 494a13 ">Refs 4th c.BC+]; ball of the hand (below the thumb), [Refs 2nd c.AD+]; palm, uncertain in [Refs 5th c.BC+]
__III.3 swelling, tumour, ἐν τῷ ἥπατι [Refs 2nd c.AD+]
__IV breastshaped hill or bank, [στῆθος">Refs 2nd c.BC+] has pan-Hellenic η, [Refs 7th c.BC+]