a river in S central South America, flowing SE from S Bolivia along the boundary between Paraguay and Argentina to the Paraguay River at Asunción. 1000 mi. (1610 km) long.
Pil·co·ma·yo (pĭl'kō-mä'yō, pēl'-) A river of central South America rising in central Bolivia and flowing about 1,609 km (1,000 mi) southeast along the Argentina-Paraguay border to the Paraguay River.