The Collaborative International Dictionary of English v.0.48:

Pinus \Pi"nus\, n. [L., a pine tree.] (Bot.)
   A large genus of evergreen coniferous trees, mostly found in
   the northern hemisphere. The genus formerly included the
   firs, spruces, larches, and hemlocks, but is now limited to
   those trees which have the primary leaves of the branchlets
   reduced to mere scales, and the secondary ones (pine needles)
   acicular, and usually in fascicles of two to seven. See
   Pine.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Pinus
    n 1: type genus of the Pinaceae: large genus of true pines [syn:
         Pinus, genus Pinus]