A lightweight boxer is a professional boxer who competes in the lightweight division, which is a weight class between 130 and 135 pounds. The two crossword solutions for this term are 'PUP' and 'PUPPY'. PUP is a three-letter word that is used to refer to a young dog or other animal, while PUPPY is a five-letter word that is used to refer to a young dog. Therefore, these two words can be used to describe a lightweight boxer, as they are both terms used to refer to a young and small creature.