Lexical Definition

‎ἐπισκιάζω‎ episkiázō (ep-ee-skee-ad'-zo) to overshadow ^G:V
from ‎ἐπί‎ and a derivative of ‎σκιά‎

overshadow.

• to cast a shade upon, i.e. (by analogy) to envelop in a haze of brilliancy
• figuratively, to invest with preternatural influence

Abbott-Smith

ἐπι-σκιάζω [in LXX: Ex 40:29(35) (שָׁכַן), Ps 90(91):4* 139(140):7* (סָכַךְ), Pr 18:11 * ;]
to throw a shadow upon, overshadow: c. dat., Ac 5:15; of a shining (Mt, l.c., and cf. Ex 40:29*, 35, II Mac 2:8) cloud, c. dat., Mk 9:7; c. acc, Mt 17:5, Lk 9:34; metaph. (cf. Pss, Pr, ll.c.), of the Holy Spirit, Lk 1:35.†

Abbott-Smith References

Liddell-Scott-Jones

ἐπισκιάζω-άζω,

throw a shade upon, overshadow, τῇ [πτέρυγι] τὴν Ἀσίην [NT+5th c.BC+]:—passive, [Refs 1st c.AD+]; opposed to φωτίζειν, [Refs 2nd c.AD+] —middle, -σκιάζεσθαι τὸν ἥλιον to ward off the sun's rays, [Refs]: metaphorically, conceal, obscure, ἀλήθειαν πλάσμασι μυθικοῖς [Refs 1st c.AD+]; τὰ δεινὰ ἑτέροις ὀνόμασιν ἐ. [Refs 2nd c.AD+]; τὴν θωπείαν, τὸν βίον, [Refs 2nd c.AD+]:—passive, τῇ εὐγενεία [Refs 2nd c.AD+]; λαθραῖον ὄμμ᾽ ἐπεσκιασμένη keeping a hidden watch, [Refs 5th c.BC+]

__2. darken, obscure, [Refs 1st c.AD+]: metaphorically, ἀφροσύνη ἐ. ψυχήν [Refs]
__3. of the Divine presence, overshadow for protection, etc., τινί [LXX]; ἐπὶ τὴν κεφαλήν τινος[NT]
__4. passive, to be weak-sighted, [Refs 2nd c.AD+]

_{LSJ Scripture Refs: Matt.17.5 ☩ Mark.9.7 ☩ LXX.Ps.90.4* ☩ Luke.1.35}