The Catholic Encyclopedia, Volume 14: Simony-Tournon

Simony is usually defined "a deliberate intention of buying or
selling for a temporal price such things as are spiritual of
annexed unto spirituals". While, this definition only speaks of
purchase and sale, any exchange of spiritual for temporal things
is simoniacal. Nor is the giving of the temporal as the price of
the spiritual required for the existence of simony; according to
a proposition condemned by Innocent XI (Denzinger-Bannwart, no.
1195) it suffices that the determining motive of the action of
one party be the obtaining of compensation from the other.