The word "bony structure" refers to the skeletal framework of a living entity. The antonyms for this term would denote the opposite conditions of the skeletal system. The antonyms might include fleshy, fleshy structure, or muscular. A fleshy structure would suggest an organism that has more soft tissues than bones. Muscular, on the other hand, would indicate that the organism's tissues are composed of more muscle mass than bone. Additionally, other antonyms could include padded, cushy, or soft structure which would indicate that the organism's skeletal system is not discernible or is underdeveloped. Ultimately, antonyms for bony structure refer to the absence or underdevelopment of bones in the organism.