PIN DOWN is a phrase that means to LOCATE or identify something precisely, or to firmly establish something. The term can be broken down into four words: LOCATE (6 letters), SET (3 letters), PEG (3 letters), and NAIL (4 letters). To 'LOCATE' something means to find it or determine its position. To 'SET' something means to put it in a particular place or position. To 'PEG' something means to fix it firmly in place. To 'NAIL' something means to fasten it securely. Together, these words create the phrase PIN DOWN, which means to LOCATE or identify something precisely, or to firmly establish something.