NOUN (3)

1. a mass of fungal tissue that has spore-bearing structures embedded in it or on it;

2. the dense colorless framework of a chloroplast;

3. the supporting tissue of an organ (as opposed to parenchyma);

The Collaborative International Dictionary of English v.0.48:

Stroma \Stro"ma\, n.; pl. Stromata. [L., a bed covering, Gr. ?
   a couch or bed.]
   1. (Anat.)
      (a) The connective tissue or supporting framework of an
          organ; as, the stroma of the kidney.
      (b) The spongy, colorless framework of a red blood
          corpuscle or other cell.
          [1913 Webster]

   2. (Bot.) A layer or mass of cellular tissue, especially that
      part of the thallus of certain fungi which incloses the
      perithecia.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stroma
    n 1: a mass of fungal tissue that has spore-bearing structures
         embedded in it or on it
    2: the dense colorless framework of a chloroplast
    3: the supporting tissue of an organ (as opposed to parenchyma)