The Collaborative International Dictionary of English v.0.48:

Anastomosis \A*nas`to*mo"sis\, n.; pl. Anastomoses. [NL., fr.
   Gr. ? opening, fr. ? to furnish with a mouth or opening, to
   open; ? + ? mouth: cf. F. anastomose.] (Anat. & Bot.)
   The inosculation of vessels, or intercommunication between
   two or more vessels or nerves, as the cross communication
   between arteries or veins.
   [1913 Webster]

WordNet (r) 3.0 (2006):

anastomosis
    n 1: a natural or surgical joining of parts or branches of
         tubular structures so as to make or become continuous [syn:
         anastomosis, inosculation]