The antonyms for the word "in-folding" include "out-folding," "unfolding," "expanding," "stretching," "extending," "spreading out," and "flattening." These terms imply the opposite of "in-folding," which is to open or flatten an object or material. In the context of biological processes, the opposite of "in-folding" could be "out-folding," where a cell membrane protrudes outward instead of inward. Similarly, in physics and engineering, the opposite of "in-folding" might be "expanding" or "stretching," where a material is pulled apart or stretched out rather than being crumpled or bent.