The term 'make plump' can be summarized by the crossword solution 'FATTEN, ' which is a 6-letter word. Fattening is a process of adding weight to an animal or food product, usually through the addition of fat or other nutrients. It is commonly used in the meat industry to increase the size and weight of animals before they are slaughtered. Fattening is also used in the food industry to make products more appealing to consumers.