The term NEIGHBOR OF ARG. can be solved by two three-letter crossword solutions: BOL and URU. Bolivia, which is represented by the letters BOL, is a landlocked country located in South America, bordered by Argentina to the south and southwest, Brazil to the north and east, Paraguay to the southeast, and Chile to the west. Uruguay, represented by the letters URU, is a country located in the southeastern part of South America, bordered by Argentina to the west and Brazil to the north, east, and south. Therefore, Bolivia and Uruguay are both neighbors of Argentina.