"Priest" (Greek kiereus, from hieros, "holy") means "priest," "minister," "presbyter," "shepherd.
"The Great Priest" is Jesus Christ who perfectly knew and embodied the Will of God, His Commandments, and by His teaching and holy way of life He performed the priestly ministry, i.e. He became to the nations a spiritual Shepherd, a Priest, Who opened to the nations the Path to holiness, separation from sin.