glomerulus

from WordNet (r) 3.0 (2006)

glomerulus
    n 1: a small intertwined group of capillaries in the malpighian
         body; it filters the blood during urine formation

from The Collaborative International Dictionary of English v.0.48

Glomerulus \Glo*mer"u*lus\, n.; pl. {Glomeruli}. [NL., dim. of
   L. glomus. See 3d {Glome}.] (Anat.)
   The bunch of looped capillary blood vessels in a Malpighian
   capsule of the kidney.
   [1913 Webster]