The Collaborative International Dictionary of English v.0.48:

Mosquito \Mos*qui"to\ (m[o^]s*k[=e]*t[-o]), n.; pl. Mosquitoes
   (m[o^]s*k[=e]*t[=o]z). [Sp. mosquito, fr. moscafly, L. musca.
   Cf. Musket.] (Zool.)
   Any one of various species of gnats of the genus Culex and
   allied genera. The females have a proboscis containing,
   within the sheathlike labium, six fine, sharp, needlelike
   organs with which they puncture the skin of man and animals
   to suck the blood. These bites, when numerous, cause, in many
   persons, considerable irritation and swelling, with some
   pain. The larvae and pupae, called wigglers, are aquatic.
   [Written also musquito.]
   [1913 Webster]

   Mosquito bar, Mosquito net, a net or curtain for
      excluding mosquitoes, -- used for beds and windows.

   Mosquito fleet, a fleet of small vessels.

   Mosquito hawk (Zool.), a dragon fly; -- so called because
      it captures and feeds upon mosquitoes.

   Mosquito netting, a loosely-woven gauzelike fabric for
      making mosquito bars.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mosquito
    n 1: two-winged insect whose female has a long proboscis to
         pierce the skin and suck the blood of humans and animals