The Collaborative International Dictionary of English v.0.48:

Dog Star \Dog" Star`\
   Sirius, a star of the constellation Canis Major, or the
   Greater Dog, and the brightest star in the heavens; -- called
   also Canicula, and, in astronomical charts, [alpha] Canis
   Majoris. See Dog days.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Canicula \Ca*nic"u*la\, n. [L. canicula, lit., a little dog, a
   diminutive of canis dog; cf. F. canicule.] (Astron.)
   The Dog Star; Sirius.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Canicula
    n 1: the brightest star in the sky; in Canis Major [syn:
         Sirius, Dog Star, Canicula, Sothis]