1) reverend, venerable
2) the title of the Roman emperors
2a) Augustan, i,e, taking its name from the emperor
2b) a title of honour which used to be given certain legions, or cohorts, or battalions, "for valour"
Part of Speech: adjective
Citing in TDNT: 7:174, 1010
From G4573; venerable (august), that is, (as noun) a title of the Roman Emperor, or (as adjective) imperial: - Augustus (-').
These two sites give similar information, with the definition from several dictionaries and statistics on the use of the word.
Perseus Digital Library
University of Chicago's Logion lexicon
Thayer's dictionary plus other information.
From this site's dictionary (in Italian)
Click on the first column to search for that word as a form of the root Σεβαστός; click on the second column to search for that grammatical form of the root Σεβαστός; click on the third column to search for that word and grammatical form; click on the total to search for the root Σεβαστός.