Built-in is a term that refers to an object, feature, or system that is integrated into another. However, its antonyms are words that describe something that is not integrated or included. Some antonyms for built-in are detached, unattached, unconnected, unrelated, and separate. These words denote a lack of integration, such as a separate accessory or an unrelated component. The opposite of built-in can also entail a lack of permanence or stability, such as a temporary or easily separable device. Knowing the antonyms of built-in can help in understanding how objects or systems are constructed, their components, and their modes of operation.