Source : Webster's Revised Unabridged Dictionary (1913)

Superimpose \Su`per*im*pose"\, v. t. [imp. & p. p.
   {Superimposed}; p. pr. & vb. n. {Superimposing}.]
   To lay or impose on something else; as, a stratum of earth
   superimposed on another stratum. -- {Su`per*im`po*si"tion},
   n.

Source : WordNet®

superimposed
     adj 1: added or imposed without integration; "the superimposed
            symbolism lacked validity"; "superimposed periodic
            variation"
     2: placed on or over something else; "an overlying image" [syn:
         {overlying}]
     3: with one layer on top of another; "superimposed rocks" [syn:
         {layered}]