A spiritual director is not the same as a confessor. Some spiritual directors are priests, but some are not. If your spiritual director is a priest, you can make your confession to him in the context of spiritual direction, but confession and spiritual direction are really different things.
As for a definition, I offer you this one from Rev. Thomas Dubay, in his book Seeking Spiritual Direction:
“What, then, is spiritual direction? It is the guiding of a person into a life truly under the dominion of the Holy Spirit, who is the primary director. It helps the directee to be more and more docile to the light and promptings of the divine Sanctifier, identifying impediments to this, as well as ways to overcome them, giving instruction and encouragement in living a life of virtue, and assisting the directee to advance on the path of prayer — the road to union with God.”
From my own experience, a meeting with my spiritual director can include discussion of my prayer life, relationships (with family and others), discerning God’s will for me, how to grow in virtue or overcome sin, the role of suffering in my spiritual life, and any other topics that impact on my relationship with God. Since my spiritual director is a priest, I usually do include sacramental confession in our meeting.