Definition of sixer:
(n) :
(cricket, colloquial) A shot in which the ball passes over the boundary without touching the ground, for which the batting team is awarded six runs.
(n) :
A Cub Scout or Brownie who leads a group of six.
(n) :
(slang) A prison sentence of six months.
(n) :
(slang) A six-pack of a beverage.
(n) :
(UK) A conker that has won six matches.
(n) :
(India) A transgender person