betting ticket; betting slip
Specifically a ticket purchased at a horse race track or off-track betting facility. The term is strongly associated with horse racing.
He bought a betting ticket at the racecourse.
My betting ticket won, and I got a considerable amount of money.
I went with a friend to buy horse racing tickets.
For the first time in a while, my ticket won and I was thrilled.
All of today's tickets ended up losing.
He picked the winning combination in a difficult race.
馬券 is counted with 枚, the standard counter for thin, flat objects like tickets and papers.
Compound of 馬 (uma, 'horse') and 券 (ken, 'ticket'). The reading ばけん is a standard Sino-Japanese compound reading.