1.the quality or fact of being prudent.
2.caution with regard to practical matters; discretion.
3.regard for one's own interests.
4.provident care in the management of resources; economy; frugality.
Lucius Malfoy and the word 'prudent' seem to fit together like peanut butter and jelly. In one of my most recent chapter readings of Chamber of Secrets (At Flourish & Blotts), Malfoy expressed wanting to use prudence as he spoke to Draco about Harry.
When I came across the specific line ('And, I would remind you that it is not - prudent - to appear less than fond of Harry Potter...'), I was surprisingly struck by how a man - who is revered as Slytherin, cunning, and generally not one to be messed with - is always waiting for the other ball to drop.
Out of all that we may see in the series of who is cautious of what is around the bend with Harry vs Voldemort, it's interesting how a death eater (in hiding, technically) cautiously takes so many precautions to protect himself and his own.
Lucius really isn't like the other death-eaters. Snape protects Harry but is proactive with Voldemort. Bella knows no bounds of being loyal to Voldy, etc. - or even those who are trying to stop evil . And Dumbledore is no doubt a master of diving deep into political situations and covering his tracks.
From the point of view of Harry, Ron, the Weasleys, etc., the Malfoys 'count' on their reputation of foxlike aggressiveness to not be messed with. Yet for a man who is so in depth of danger by working with Voldemort, he is so discreet in his precautions and yet not.