Source : Webster's Revised Unabridged Dictionary (1913)

Insecta \In*sec"ta\, n. pl. [NL. See {Insect}.]
   1. (Zo["o]l.) One of the classes of Arthropoda, including
      those that have one pair of antenn[ae], three pairs of
      mouth organs, and breathe air by means of trache[ae],
      opening by spiracles along the sides of the body. In this
      sense it includes the Hexapoda, or six-legged insects and
      the Myriapoda, with numerous legs. See {Insect}, n.

   2. (Zo["o]l.) In a more restricted sense, the Hexapoda alone.
      See {Hexapoda}.

   3. (Zo["o]l.) In the most general sense, the Hexapoda,
      Myriapoda, and Arachnoidea, combined.

   Note: The typical Insecta, or hexapod insects, are divided
         into several orders, viz.: {Hymenoptera}, as the bees
         and ants; {Diptera}, as the common flies and gnats;
         {Aphaniptera}, or fleas; {Lepidoptera}, or moths and
         butterflies; {Neuroptera}, as the ant-lions and
         hellgamite; {Coleoptera}, or beetles; {Hemiptera}, as
         bugs, lice, aphids; {Orthoptera}, as grasshoppers and
         cockroaches; {Pseudoneuroptera}, as the dragon flies
         and termites; {Euplexoptera}, or earwings; {Thysanura},
         as the springtails, podura, and lepisma. See these
         words in the Vocabulary.

Source : WordNet®

Insecta
     n : insects; about five-sixths of all known animal species [syn:
          {class Insecta}, {Hexapoda}, {class Hexapoda}]