Super armor (or “armor”) is a special kind of hitbox that shrugs off attacks.
Ignores effects from most attacks (such as pushback) other than damage.
In the Marvel series, in which the first implementation of super armor is found, usually, other than specific attacks enveloping the body (jumping strong attacks and crouching strog kicks), attacks were treated such that if one does not pile on continuous attacks, there would be no pushback; however, in more recent years, this has become a hitbox where even if one takes an attack at the outset, there will not be pushback.
Jin Saotome’s strong attacks and Street Fighter IV’s armor break attribute moves are examples; there are also attacks that have the property of invalidating these.