Of a position, privilege etc.: available for purchase rather than assigned on merit.
2002, (w), The Great Nation, Penguin 2003, p. 140:
Thus, regimental commands in the army were – as with the judiciary or the financial bureaucracy – venal posts, which were purchased, bequeathed and sold among the nobility.
Capable of being bought (of a person); willing to take bribes.
Though there is a disposition in mankind, to declaim against the corruption and peculation of the present times, as being more venal than formerly; yet, if we look back to different periods, we shall find statesmen and politicians, as selfish and corrupt, (...) as those who have lately figured on the political stage.