The antonyms for the phrase "cut down size" are expand, increase, enhance, amplify, and enlarge. These words signify a growth in size or quantity, as opposed to a decrease. When a business is expanding, for instance, it means that they are increasing their reach or production. Similarly, when a person is enhancing their skills, it means that they are improving their abilities. Amplifying a product's features means that it is becoming more powerful or effective. Enlarging a home means that it is becoming more spacious. The antonyms for "cut down size" denote growth and improvement, rather than reduction.