Superseding indictment is an indictment that is filed subsequent to an original indictment. It is usually based upon supervening events that logically change the nature of the original indictment.
Example: A stabs B. B survives the wound because of medical intervention, without which he would have died. A was indicted for, say, frustrated homicide. After indictment, B dies as a direct result of the complications in the wound. The original indictment for frustrated homicide may be set aside, as the victim had actually died, and a superseding indictment may now be allowed based on this supervening event, e.g. the subsequent death of B, and qualify the indictment for consummated homicide, instead of frustrated homicide.