The Collaborative International Dictionary of English v.0.48:

achondroplasia \achondroplasia\ n. (Med.)
   A skeletal disorder beginning before birth; cartilage is
   converted to bone resulting in dwarfism.
   [WordNet 1.5]

WordNet (r) 3.0 (2006):

achondroplasia
    n 1: an inherited skeletal disorder beginning before birth;
         cartilage is converted to bone resulting in dwarfism [syn:
         achondroplasia, achondroplasty, osteosclerosis
         congenita, chondrodystrophy]