1) a drinking party, entertainment
1a) of the party itself, the guests
1b) rows of guests
Part of Speech: noun neuter
Neuter of a derivative of the alternate of G4844; a drinking party ("symposium"), that is, (by extension) a room of guests: - company.
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 συμπόσιον; click on the second column to search for that grammatical form of the root συμπόσιον; click on the third column to search for that word and grammatical form; click on the total to search for the root συμπόσιον.