The Rheims translation says (Vulgate translation and Greek in parentheses):
And the lord commended the unjust steward, forasmuch as he had done wisely (prudenter, φρονίμως): for the children of this world are wiser (prudentiores, φρονιμώτεροι) in their generation than the children of light.
Behold I send you as sheep in the midst of wolves. Be ye therefore wise (prudentes, φρόνιμοι) as serpents and simple as doves.
Prudens means "foreseeing, foreknowing", and φρόνιμος means "in one's right mind, in one's senses".
St. Thomas explains this prudence/wisdom in his commentary on Matthew 10:
Be ye wise. The prudence of a serpent consists in that it always wishes to defend its head. The head is Christ, whom He commands them to serve. Hence: “I have fought a good fight: I have finished my course: I have kept the faith” (II Tim. 4, 7). Likewise, they ought to guard the Head, because it is the principle of the whole (I Cor. 11, 3);23 “With all watchfulness keep thy heart” (Prov. 4, 23). Likewise, there is another prudence of a serpent, that when it grows old, it passes through a narrow hole and sheds its vesture, or skin; so we ourselves ought to do in relation to our manner of living. And the Apostles says: “Stripping yourselves of the old man with his deeds,” etc., (Col. 3, 9). Moreover, we ought to have a serpent’s prudence in preaching, because, as it is stated in Gen. 3, on account of the serpent’s shrewdness, the human race was cast down, because he attacked the weaker sex. Likewise, he showed her a tree. So preachers ought to convert sinners through the most apt means. Similarly, they ought to exhort concerning the tree of the Cross, so that just as the devil derived benefit from a tree for an evil end, so these men ought to derive benefit from the tree of the Cross for a good end.