The term 'WHAT HULKS PUMP' can be solved by the four-letter word 'IRON'. IRON is a chemical element with the symbol Fe and atomic number 26. It is a metal that is found in the Earth's crust and is one of the most abundant elements. IRON is used in many industries, including construction, manufacturing, and transportation. It is also used to make tools, weapons, and other items. In addition, IRON is an important component of hemoglobin, which carries oxygen in the blood.