Is a son's saying to his mother, "What is this ignorance?" considered an act of disobedience (ʿuquq), and is an apology sufficient to absolve him before God, or must he do something else to remove the effect of this word?

Describing one's mother as ignorant is an act of disobedience (uquq), and it goes against the good manners, gentleness, humility, and reverence required towards parents. It also prohibits scolding them or speaking harshly to them. Anything that harms parents, whether it be through communication styles, belittling, or disparagement, is considered an act of disobedience. If he apologizes to her and she forgives him, that is sufficient, and he must strive to please her, because Allah's pleasure is linked to the pleasure of parents.