Kiddushin 45 - Betrothal by a Minor without the Knowledge of Her Father
A minor who became betrothed without the knowledge of her father requires a Get before she can marry another man, for the eventuality that her father has agreed to her betrothal and it became valid. She also requires "Refusal", a procedure where the minor says to her husband in court "I do not want you anymore" in case her father has not agreed.
A certain man betrothed a minor by giving her a bundle of vegetables in the marketplace. Here we are not concerned that the father may acquiesce, because betrothal was not done honorably.