The Collaborative International Dictionary of English v.0.48:

Canaliculus \Can`a*lic"u*lus\, n.; pl. Canaliculi. [L.]
   (Anat.)
   A minute canal.
   [1913 Webster]

WordNet (r) 3.0 (2006):

canaliculus
    n 1: a small canal or duct as in some bones and parts of plants