Lexical Definition

‎ἀπαύγασμα‎ apaúgasma (ap-ow'-gas-mah) radiance ^G:N-N
from a compound of ‎ἀπό‎ and ‎αὐγάζω‎

brightness.

• an off-flash, i.e. effulgence

Abbott-Smith

**† ἀπ-αύγασμα, -τος, τό (< αὐγή, brightness, whence ἀπαυγάζω, to radiate or reflect), [in LXX: Wi 7:26*;]
of light beaming from a luminous body, radiance, effulgence: He 1:3.†

Abbott-Smith References

Liddell-Scott-Jones

ἀπαύγασμα-ασμα, ατος, τό,

radiance, effulgence, of light beaming from a luminous body, φωτὸς ἀϊδίου[LXX+NT+1st c.AD+]

_{LSJ Scripture Refs: Heb.1.3}