A weekend in which one does nothing productive and has little social interaction with others. For a true french weekend, one must not leave one's home/dorm at all on Friday or Saturday. Usually, one gets more than 24 hours of sleep on friday and saturday nights combined. Lots of leftover food, ramen noodles, and/or Domino's is consumed. Personal hygiene is neglected; Masturbation occurs frequently. French weekends wind down on Sunday afternoon, when one cleans one's living quarters and takes an excessively long shower, in which the balls are washed thoroughly. Only after this thorough washing of the balls may homework or any preparation for the week ahead begin.
If Valentines day falls on a weekend, your partner has to spend the whole weekend with you, because then the whole weekend is seen as a big Valentines day.