When you come back to school or work from your vacation and you can't remember what you did before your vacation.
Andy suffered from a bad case of vacation amnesia when he went back to school and couldn't remember what he had been learning before.
Someone who actually uses the Urban Word of The Day words in everyday talk. In doing so he/she sounds like a douche.
Husband: "Honey, I just played Russian Toilette, and lost"
Wife: "Don't be an Urban Dictionary Douche!"