The Collaborative International Dictionary of English v.0.48:

Supercharge \Su`per*charge"\, v. t. [imp. & p. p.
   Supercharged; p. pr. & vb. n. Supercharging.] [Pref.
   super- + charge. Cf. Surcharge.] (Her.)
   To charge (a bearing) upon another bearing; as, to
   supercharge a rose upon a fess.
   [1913 Webster]