The common definition, able to act or not when all requisites are present, has a good sense: simultaneity of power, not power of simultaneity
The common definition places human freedom in a man's being able, when everything needed for acting is present, to act or not act, or to do this or that. Some misuse it, but it can bear a good and suitable sense.
In all deliberate actions, which alone are free in the proper and strict sense, a man has a true and real power not to act or to act otherwise, not only before he acts but while he is acting. He cannot, of course, do two opposite things at once, or act and stop acting at the same time. Yet while he does the one, the power for the opposite act, or for stopping, remains in him.
The schoolmen express this by saying that free choice has a simultaneity of power for opposites, but not a power of simultaneity, that is, a power to have the opposites at once. The reason is that a power for one act is not opposed to a power for not doing it or for doing the contrary, whereas two contraries or contradictories cannot be in the same subject at once.
Latin
XXIX. Proinde vulgata illa definitio, juxta quam libertas humana in eo statuitur, quod positis omnibus ad agendum requisitis, homo possit agere, vel non agere, hoc aut illud agere, licet quidam ea abutantur, bonum tamen & commodum sensum habere potest. Nam in actionibus omnibus deliberatis, quae solae proprie & stricte liberae sunt, homo non solum antequam agat, sed etiam dum agit, habet veram & realem potentiam non agendi, aut aliter agendi. Non potest quidem homo agere duo opposita simul, aut simul & agere & ab actione cessare: Sed tamen quum hoc agit, manet in eo potestas ad actum oppositum, aut ad cessationem ab illa actione. Quod Scholastici dicunt in libero arbitrio esse simultatem potentiae ad opposita, sed non potentiam simultatis, id est, potentiam ad opposita simul habenda. Cujus rei ratio est, quia potentia ad unum actum non opponitur potentiae ad illius actus negationem aut ad actum contrarium; sed duo contraria, aut contradicentia non possunt esse simul in eodem subjecto.