Lexical Definition

‎φωστήρ‎ phōstḗr (foce-tare') light ^G:N-M
from ‎φῶς‎

light.

• an illuminator, i.e. (concretely) a luminary, or (abstractly) brilliancy

Abbott-Smith

φωστήρ, -ῆρος, ὁ (< φῶς), [in LXX: Ge 1:14, 16 (מָאוֹר), Da LXX 12:3 (זֹהַר), I Es 8:79, Wi 13:2, Si 43:7 * ;]
a luminary, light: Phl 2:15, Re 21:11.†
SYN.: φέγγος, φῶς

Abbott-Smith References

Liddell-Scott-Jones

φωστήρ, ῆρος, ὁ,

that which gives light, οἱ φ. the lights of heaven, stars, [LXX+4th c.BC+]; οἱ δύο φ., i.e. sun and moon, [NT+5th c.AD+]

__2 splendour, radiance, ὁ φ. αὐτῆς ὅμοιος λίθῳ τιμιωτάτῳ [NT]
__3 metaphorically, of a king, τῷ φ. τῷ ἡμετέρῳ [Refs 4th c.AD+]
__4 of the eyes, [Refs 2nd c.AD+]
__II opening for light, door or window, [Refs 5th c.AD+]

_{LSJ Scripture Refs: Phil.2.15 ☩ Rev.21.11}