Source : Free On-Line Dictionary of Computing

outline font
     
         (Or "vector font") A {font} defined as a set of lines
        and curves as opposed to a {bitmap font}.  An outline font
        (e.g. {PostScript}, {TrueType}, {RISC OS}) can be scaled to any
        size and otherwise transformed more easily than a bitmap font,
        and with more attractive results, though this requires a lot
        of numerical processing.  The result of transforming a
        character in an outline font in a particular way is often
        saved as a bitmap in a {font cache} to avoid repeating the
        calculations if that character is to be drawn again.
     
        (1995-03-16)