The Collaborative International Dictionary of English v.0.48:

magnifying glass \magnifying glass\ n.
   A single convex lens which magnifies the apparent dimensions
   of objects seen through it, and is used to produce an
   enlarged image.

   Syn: hand glass.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

magnifying glass
    n 1: light microscope consisting of a single convex lens that is
         used to produce an enlarged image; "the magnifying glass
         was invented by Roger Bacon in 1250" [syn: hand glass,
         simple microscope, magnifying glass]