The Monado Art Run Cancel, or MARC, is a Smash 4 advanced technique that is essentially a dash cancel. It uses the cancellation of an Art to negate the ending lag/braking animation of the character's run in order to instantly change their running direction, or to perform tilts immediately out of a run. This allows the user to weave in-and-out to bait attacks or options and punish them, such as baiting out a jump and punishing with an instant up-tilt out of the MARC.
In Ultimate, the universal dash cancel eliminates the need of this technique.
Though clips of the tech had been seen prior, MARC was first explained by Catalyst.