Something malformed has a shape that's twisted or warped, or otherwise distorted. Your first try at making pottery might result in a couple of malformed bowls.
If you leave a doll in the hot sunlight for hours, she may melt and become malformed. Sometimes parts of the body are malformed because of birth defects or accidents. If you're born with a malformed spine, you may wear a brace to straighten it out. If your feet are malformed, your choice of shoes will be limited. Malformed combines the prefix mal-, "badly or wrongly," with formed, from the Latin forma, "shape or appearance."