قلب is an Arabic word meaning "Heart". It is the second among the six purities or Lataif-e-sitta in Sufi philosophy.
Definition #2 for "Qalb"
Center of Intelligence, that is Brain. In Islamic philosophy, the qalb (Arabic: قلب), or heart, is the origin of intentional activities, the cause behind all of humans intuitive deeds. While the brain handles the physical impressions, qalb (the heart) is responsible for apprehending. Heart and brain work together, but it is the heart where true knowledge can be received.