Source : Webster's Revised Unabridged Dictionary (1913)

Diverticulum \Div`er*tic"u*lum\, n.; pl. {Diverticula}. [L. See
   {Diverticle}.] (Anat.)
   A blind tube branching out of a longer one.

Source : WordNet®

diverticulum
     n : a herniation through the muscular wall of a tubular organ
         (especially the colon)
     [also: {diverticula} (pl)]