Firedashing is a mostly useless Fox technique discovered by Hylian that involves using Firefox to bounce off of the stage and edgehog.
To perform the technique, the player stands on the stage, facing the target ledge. They then jump and up+B diagonally into the stage, heading towards the ledge. Upon collision, Fox will bounce off the stage and, if spaced properly, fall right to the edge. If you hold the control stick back (towards the edge) as Fox falls past it, he will grab onto the edge, thus edgehogging.
However, given that the technique requires incredibly precise spacing, anyone who can aim Firefox that well could just as easily (more easily?) simply up+B directly to the ledge, because Fox/Falco's up+B will grab onto the edge from any direction as long as the control stick is tilted towards the ledge when they encounter its sweetspot radius.