2) the second of the first Sabbaths after the feast of the Passover
Part of Speech: adjective
From G1208 and G4413; second first, that is, (specifically) a designation of the Sabbath immediately after the Paschal week (being the second after Passover day, and the first of the seven Sabbaths intervening before Pentecost): - second . . . after the first.
|the second after the first||61.12|
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 δευτερόπρωτος; click on the second column to search for that grammatical form of the root δευτερόπρωτος; click on the third column to search for that word and grammatical form; click on the total to search for the root δευτερόπρωτος.