a river in S central South America, rising in W central Bolivia and flowing southeast, forming the border between Argentina and Paraguay, to the Paraguay River at Asunción. Length: about 1600 km (1000 miles)
Pilcomayo in American English
(ˌpilkɔˈmɑjɔ)
river flowing from S Bolivia southeast along the Argentine-Paraguayan border intothe Paraguay River, near Asunción: c. 1,000 mi (1,609 km)