A "priest" is a person who has authority to perform certain rites and rituals in some religions. "to consecrate" means to make something holy or sacred. "baptismal" is the adjectival form of the word "baptism". "baptism" is the ceremony or rite performed in some religions in which a person's body or head is immersed in water. Baptism symbolizes the person's acceptance into the particular church or faith. A "basin" is an open, usually round container for holding water. In some religions, a person is baptized using "holy water" (water that has been blessed (made sacred) by the priest. So: The priest blessed the water that was in the container (the baptismal basin) that is used to perform baptisms.