1. To handle or deal with someone or something with a particular type of attitude or behavior. He has treated me with nothing but contempt since I got the promotion. Students who treat this project with indifference will suffer the consequences in their grades.

2. To attempt to reach an agreement or settlement with someone, as through negotiations. Police are treating with the criminals to avoid any casualties among the hostages. We refuse to treat with any nation that does not give its citizens basic human rights.