Definition of 21:
(N) :
(twenty-one) the natural number following 20 and preceding 22.
(N) :
21, Bagram, or Twenty Plus One is a drinking game.
(N) :
the second studio album by American R&B singer Omarion.
(N) :
"21" is the debut single by The Paddingtons, released on 11 October 2004, which was later re-recorded for the album First Comes First.
(N) :
a 2008 American heist drama film directed by Robert Luketic and distributed by Sony Pictures Releasing.
(N) :
the second studio album by the English singer-songwriter Adele.