The Catechism of the Catholic Church defines simony generically as the buying and selling of spiritual things.

This may includes the priesthood itself.  So the Second Council of Nicea, 787 AD, decries those who pride themselves that because of their benefactions of gold they were ordained in the Church, and continues:

if it appear that any one has done this [i.e., given money], at any time as a price for ordination, let him be dealt with according to the Apostolic Canon which says: "If  a bishop has obtained possession of his dignity by means of money (the same rule applies also to a presbyter or deacon) let him be deposed and also the one who ordained him, and let him also be altogether cut off from  communion, even as Simon Magus was by Peter." To the same effect is the second canon of our holy fathers of Chalcedon, which says: If any bishop gives ordination in return for money, and puts up for sale that which  cannot be sold, and ordains for money a bishop or chorepiscopus, or presbyter, or deacon, or any other of those who are reckoned among the clergy; or who for money shall appoint anyone to the office of oeconomus, advocate, or  paramonarius; or, in a word, who hath done anything else contrary to the canon, for the sake of filthy lucre--he who hath undertaken to do anything of this sort, having been convicted, shall be in danger of losing his degree. And he who has been ordained shall derive no advantage from the ordination or promotion thus negotiated; but let him remain a stranger to the dignity and responsibility which he attained by means of money .