hy·a·lu·ron·ic acid 
(hī′ə-l-rŏnĭk)
(hī′ə-l-rŏnĭk)n.
A glycosaminoglycan that is found in extracellular tissue space, the synovial fluid of joints, and the vitreous humor of the eyes and acts as a binding, lubricating, and protective agent.
[Greek hualos, glass + -URONIC.]