The Collaborative International Dictionary of English v.0.48:

Cellulitis \Cel`lu*li"tis\, n. [NL., fr. L. cellula + -itis.]
   An inflammantion of the cellular or areolar tissue, esp. of
   that lying immediately beneath the skin.
   [1913 Webster]

WordNet (r) 3.0 (2006):

cellulitis
    n 1: an inflammation of body tissue (especially that below the
         skin) characterized by fever and swelling and redness and
         pain