1) a night and a day, the space of twenty four hours
Part of Speech: noun neuter
From G3571 and G2250; a day and night, that is, full day of twenty four hours: - night and day.
|a night and a day||67.179|
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 νυχθήμερον; click on the second column to search for that grammatical form of the root νυχθήμερον; click on the third column to search for that word and grammatical form; click on the total to search for the root νυχθήμερον.