From The Collaborative International Dictionary of English v.0.48:
Sweepstakes \Sweep"stakes`\, n.
1. A winning of all the stakes or prizes; a sweepstake.
[1913 Webster]
2. sing. or pl. The whole money or other things staked at a
horse race, a given sum being put up for each horse, all
of which goes to the winner, or is divided among several,
as may be previously agreed.
[1913 Webster]
3. A race for all the sums staked or prizes offered.
[1913 Webster]