Invincibility

An Invincibility frame is a period of time where a character is completely invulnerable to damage, grabs, and knockback. Invincibility frames are not to be confused with knockback resistance, which only reduces or negates the effect of knockback - not damage - from an attack, or intangibility frames, where a player is, essentially, invincible, however will not receive hitlag if on the receiving end of an attack.

Characters can gain invincibility frames in a few ways. An example can be during the initial stages of a character entering their Final Form or using some other form of a Final Smash, which grants them invincibility frames as they transform or exceute their attack to prevent interruption.

Some attacks will also grant the user invincibility frames.