-achondrio-; -achondroa combining form relating to insufficient or defective cartilage. achondroplasia a form of autosomal-dominant dwarfism in which the bones derived from carbones tilage develop at a slower rate than the derived from connective tissue. This results in an enlarged cranial vault and abnormally high forehead. Motor development of infants with this disorder may be slow and the individual may or may not be mentally retarded. About one-third of one group studied had subnormal intelligence. Also called achondroplastic dwarfom. Also see DWARnsM.