A lottery was a game in which people could win money.
History
The National Lottery was a municipal lottery played in the United Kingdom. (TV: Rose, School Reunion, The End of Time)
When needing to gain access to Kazran Sardick without the interference of his staff, the Eleventh Doctor arranged for them to win the lottery, even though it did not exist. The Doctor simply called them very lucky. When Kazran ordered him out, and he travelled back to Kazran's childhood, the Doctor acted as his babysitter, after his usual babysitter won the lottery, even though it did not exist, even back then. (TV: A Christmas Carol)