Note:
Prayer in this telling is first and foremost asking for (spiritual) stuff, or expressing our desires to God. It isn’t here the sitting with God that we read about in present-day spiritual literature (note that the source of this quote is over 100 years old!). Meditation, as a subclass of prayer, is described at the end of the quote.

Quote:
“An act of the virtue of religion which consists in asking proper gifts or graces from God. In a more general sense it is the application of the mind to Divine things, not merely to acquire a knowledge of them but to make use of such knowledge as a means of union with God. This may be done by acts of praise and thanksgiving, but petition is the principal act of prayer.”

“It is therefore the expression of our desires to God whether for ourselves or others. This expression is not intended to instruct or direct God what to do, but to appeal to His goodness for the things we need….

“Meditation is a form of mental prayer consisting in the application of the various faculties of the soul, memory, imagination, intellect, and will, to the consideration of some mystery, principle, truth, or fact, with a view to exciting proper spiritual emotions and resolving on some act or course of action regarded as God’s will and as a means of union with Him. In some degree or other it has always been practised by God-fearing souls.”

Source: Wynne, John. “Prayer.” The Catholic Encyclopedia. Vol. 12. New York: Robert Appleton Company, 1911.