In secular use, meditari means, in a general way, to think, to reflect, as does cogitare or considerare; but, more than these, it often implies an affinity with the practical or even moral order. It implies thinking of a thing with the intent to do it; it other words, to prepare oneself for it, to prefigure it in the mind, to desire it, in way , to do it in advance–briefly, to practice it. 
…Another important factor explained by rumination and reminiscence is the power of imagination of the medieval man. Exuberant as this faculty is, it nevertheless possesses a vigor and a preciseness which we find difficult to understand. We are used to seeing, almost without looking at them unless with a distracted eye, printed or moving pictures. We are fond of abstract ideas. Our imagination, having become lazy, seldom allows us to do anything but dream. But in the men of the Middle Ages it was vigorous and active. It permitted them to picture, to “make present,” to see beings with all the details provided by the texts. …The words of the sacred text never failed to produce a strong impression on the mind. 
The Love of Learning and the Desire for God: A Study of Monastic Culture by Jean Leclercq.