1) a neighbour
1a) a friend
1b) any other person, and where two are concerned, the other (thy fellow man, thy neighbour), according to the Jews, any member of the Hebrew nation and commonwealth
1c) according to Christ, any other man irrespective of nation or religion with whom we live or whom we chance to meet
Part of Speech: adverb
Citing in TDNT: 6:311, 872
Neuter of a derivative of πέλας pelas (near); (adverb) close by; as noun, a neighbor, that is, fellow (as man, countryman, Christian or friend): - near, neighbour.
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 πλησίον; click on the second column to search for that grammatical form of the root πλησίον; click on the third column to search for that word and grammatical form; click on the total to search for the root πλησίον.