The Collaborative International Dictionary of English v.0.48:

Designer \De*sign"er\, n.
   1. One who designs, marks out, or plans; a contriver.
      [1913 Webster]

   2. (Fine Arts) One who produces or creates original works of
      art or decoration.
      [1913 Webster]

   3. A plotter; a schemer; -- used in a bad sense.
      [1913 Webster]

WordNet (r) 3.0 (2006):

designer
    n 1: a person who specializes in designing architectural
         interiors and their furnishings [syn: interior designer,
         designer, interior decorator, house decorator, room
         decorator, decorator]
    2: someone who creates plans to be used in making something
       (such as buildings) [syn: architect, designer]
    3: someone who specializes in graphic design [syn: graphic
       designer, designer]
    4: a person who devises plots or intrigues; "he is believed to
       be the principal designer of the terrorist bombing attack"
       [syn: designer, intriguer]
    5: someone who designs clothing [syn: couturier, fashion
       designer, clothes designer, designer]