Source : Webster's Revised Unabridged Dictionary (1913)

Microscope \Mi"cro*scope\, n. [Micro- + -scope.]
   An optical instrument, consisting of a lens, or combination
   of lenses, for making an enlarged image of an object which is
   too minute to be viewed by the naked eye.

   {Compound microscope}, an instrument consisting of a
      combination of lenses such that the image formed by the
      lens or set of lenses nearest the object (called the
      objective) is magnified by another lens called the ocular
      or eyepiece.

   {Oxyhydrogen microscope}, and {Solar microscope}. See under
      {Oxyhydrogen}, and {Solar}.

   {Simple, or Single}, {microscope}, a single convex lens used
      to magnify objects placed in its focus.

Source : WordNet®

microscope
     n : magnifier of the image of small objects; "the invention of
         the microscope led to the discovery of the cell"