A vesicle, or bubble found within a cell which was formed by pinching off the cell membrane, which is coated with the protein clathrin and contains nutrient particles, is transporting a regulatory molecule from outside the cell to its destination within the cell, or is transporting newly-made proteins to other organelles or to the outside of the cell. Coated vesicles arise from coated pits.
From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.