De-truncating refers to the process of restoring something to its original length or size. The antonyms of de-truncating would be related to shrinking or shortening something, such as truncating or reducing. Other antonyms for de-truncating might include terms such as minimizing, compressing, condensing, or abbreviating. These words refer to actions that make something smaller or more compact. When it comes to physical objects, the antonyms of de-truncating could also include words like breaking, cutting, or fragmenting, which would refer to processes that destroy, rather than restore, an object's original length or shape.