1) the setting of the sun
2) the region of the sunset, the west
Part of Speech: noun feminine
From G1416; the sun set, that is, (by implication) the western region: - west.
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 δυσμή; click on the second column to search for that grammatical form of the root δυσμή; click on the third column to search for that word and grammatical form; click on the total to search for the root δυσμή.