The crossword solution for the term 'undesired stocking stuffer' is 'COAL'. COAL is a combustible black or brownish-black sedimentary rock, formed as rock strata called COAL seams. It is mostly carbon with variable amounts of other elements, such as hydrogen, sulfur, oxygen, and nitrogen. COAL is used as a fuel source for electricity generation and industrial heating. However, it is not a desirable gift to receive during the holiday season.