A patit is an initiated Sikh who has broken one of the four grave breaches of the code, most often by cutting the hair, and the word means fallen.
The grave breaches
The standing applies specifically to one who has taken amrit and entered the Khalsa and then committed one of the cardinal violations of the code of conduct, of which the cutting of the hair is the most common, the others including the use of tobacco or intoxicants, the eating of ritually slaughtered meat, and adultery, so the patit is not one who never observed the discipline but one who accepted it and then broke it. The gravity attaches to the breach of a commitment freely taken, which is why the term marks a fall rather than a mere lapse.
Fall and restoration
The condition of the patit is not necessarily permanent, for the tradition provides a way back: one who has fallen may confess before the congregation, accept the penance imposed, and be reinitiated, so the fall from the Khalsa can be repaired through repentance and the renewal of the initiation. The existence of the category, and of the path of restoration, reflects the seriousness with which the initiation and its discipline are held, since only a commitment that binds can be broken and only a breach that matters requires restoration. The patit thus stands as the negative counterpart of the amritdhari, the initiated Sikh measured against the discipline and found to have fallen from it, with the way of return held open.