The term 'smallest in size' can be summarized as 'LEAST' which is a 5 letter word. This term is used to describe something that is the smallest in size when compared to other items. It is often used to compare the size of objects, such as the smallest house in a neighborhood or the smallest car in a parking lot. It can also be used to compare the size of animals, such as the smallest dog in a litter or the smallest fish in an aquarium.