Louche means of questionable taste or morality; decadent; disreputable or sordid (sometimes in a rakish or appealing way). It is generally used to refer to an unrespectable neighbourhood within a town or city.
It has a strange origin coming for the French for cross-eyed, squint-eyed, which in turn came from the Latin luscus blind in one eye. Presumably from the idea that people who did not look you straight in the eyes were disreputable. Its first known use was in 1819.