It most literally translates from archaic French as "valiant," and is often combined with the phrase "preux chevalier" which means "valiant knight." It's common usage in the English language may be partially attributed to the author P.G. Wodehouse in his tales of Bertram Wooster, who would have learned to always be preux in his time at Eaton and Oxford.
A true "preux chevalier" will always defend the honor of a lady.
by Andy Robinson May 31, 2006