Stronger and more formal than 坏习惯 (bad habit). 陋习 implies the practice is socially shameful or culturally backward, common in editorials about public manners, weddings, funerals, etc.
memory
陋 = crude / shabby (also in 简陋 'crude and simple', 丑陋 'ugly') + 习 = habit. A shabby habit, one that should be left in the past.
