What is "dibenzylpiperazine"

Dibenzylpiperazine (DBZP) is a piperazine derivative often found as an impurity in the recreational stimulant drug benzylpiperazine (BZP). Presence of DBZP is a marker for low quality or badly made BZP. It can be made as a reaction byproduct during BZP synthesis, either because the reaction has been run at too high a temperature, or because an excess of benzyl chloride has been used.