A re-incarnated Tibetan teacher. A tulku (also tülku, trulku) is a custodian of a specific lineage of teachings in Tibetan Buddhism who is given empowerments and trained from a young age by students of his predecessor.
High-profile examples of tulkus include the Khyentses, the Kongtruls, the Dalai Lamas and the Karmapas.
Example via www.ramdass.org: Tulku Urgyen Rinpoche
Example via www.mindpodnetwork.com: Tulku Urgyen Rinpoche On Doubt