A vessel may be defined as a hollow utensil for holding something, an object that is used as a container. Figuratively speaking, a vessel refers to a person regarded as receiving or containing something, one into whom something is conceived as poured or in whom something is stored for use.
Acts 9:15 (NKJV): But the Lord said to him, “Go, for he is a chosen vessel of Mine to bear My name before Gentiles, kings, and the children of Israel”.