1A large hoofed mammal used for riding, transport, or work; a horse.
牧場で生まれて初めて馬に乗った。
I rode a horse for the first time at the ranch.
農家では今でも馬を使って畑を耕すことがある。
Some farms still use horses to plow their fields.
あの白い馬はとても穏やかな性格だ。
That white horse has a very gentle temperament.
子供たちは動物園で馬にニンジンをあげた。
The children fed carrots to the horse at the zoo.
2Horse racing — the sport of racing horses, or activities related to it such as betting.
父は週末になるとよく馬を見に競馬場へ行く。
My father often goes to the racetrack on weekends to watch the horses.
彼は初めて馬に賭けて、思いがけず勝った。
He bet on a horse for the first time and won unexpectedly.
今年のダービーはどの馬が勝つか予想が難しい。
It's hard to predict which horse will win this year's Derby.
3In shogi, the piece a bishop becomes when promoted; written as 馬 (uma).
角が成って馬になると、斜めだけでなく縦横にも動けるようになる。
Once the bishop promotes into a 'uma', it can move not only diagonally but also vertically and horizontally.
4A card used in certain traditional Japanese card games such as mekuri karuta.
古いかるたには馬の絵が描かれた札がある。
In old karuta sets there are cards with a horse ('uma') illustration.