Lexical Definition

‎μεγαλοπρεπής‎ megaloprepḗs (meg-al-op-rep-ace') majestic ^G:A
from ‎μέγας‎ and ‎πρέπω‎

excellent.

• befitting greatness or magnificence (majestic)

Abbott-Smith

μεγαλοπρεπής, ές (= μεγάλῳ πρέπων), [in LXX: De 33:26 (גַּאֲוָה), II Mac 8:15 15:13, III Mac 2:9*;]
befitting a great man, magnificent, majestic: II Pe 1:17 (cf. MM, xvi).†

Abbott-Smith References

Liddell-Scott-Jones

μεγαλοπρεπής-πρεπής, ές,

befitting a great man, magnificent, δεῖπνον μ. [Refs 5th c.BC+]; δόξα [NT]

__2 of persons, [Refs 5th c.BC+]; of a horse, [Refs]: superlative, as honorific title, [Refs 5th c.AD+]
__3 of style, μ. λόγοι [Refs 5th c.BC+]
__II adverb -πέως, Attic dialect -πῶς[Refs 5th c.BC+]: comparative -έστερον [Refs 5th c.BC+]: superlative -έστατα [Refs 5th c.BC+]

_{LSJ Scripture Refs: 2Pet.1.17}