'Kompressor' is a German word meaning, literally, 'compressor', (big surprise), or 'squeezer'.
Mercedes-Benz use 'Kompressor' to denote the presence of a supercharger in particular model variants. At the time of writing, the one exception to the Kompressor rule in the MB stable is the SL65 AMG, which uses twin turbos to squeeze 604 hp out of a 6.0 L V-12.
It should be clarified that Mercedes-Benz do not use the letter 'K' in their model designations to indicate the presence of a supercharger. The letter 'K' stands for either Kompakt, (compact), or Kurz, (short), depending on who you listen to, (even Mercedes-Benz themselves mix and match on this last point).
For example: SLK = 'Sportlich', 'Leicht', 'Kurz/Kompakt'. This translates to 'sporty, light and short'.