Lexical Definition

‎μεγαλειότης‎ megaleiótēs (meg-al-i-ot'-ace) majesty ^G:N-F
from ‎μεγαλεῖος‎

magnificence, majesty, mighty power.

• superbness, i.e. glory or splendor

Abbott-Smith

μεγαλειότης, -ητος, ἡ (< μεγαλεῖος), [in LXX: Je 40 (33):9* (תִּפְאֶרֶת), Da LXX 7:27, I Es 1:5 4:40*;]
splendour, magnificence: Lk 9:43, Ac 19:27, II Pe 1:16 (freq. in π. as a ceremonial title, MM, xvi).†

Abbott-Smith References

Liddell-Scott-Jones

μεγαλειότης-ότης, ητος, ἡ,

majesty, magnificence, [NT+1st c.AD+]; of a person, greatness, [Refs 2nd c.AD+]

__II as a title, [Refs 1st c.AD+]; ἐν ταῖς μ. γενήσεται [Refs 2nd c.AD+]; also, = Latin majestas, ἡ μ. τοῦ Ῥωμαίων δήμου [Refs 3rd c.AD+]

_{LSJ Scripture Refs: Luke.9.43}