To go down a slope; to travel from the top to the bottom of a hill (on foot, by bicycle, car, etc.).
自転車でゆっくり坂を下りる。
Ride the bicycle down the hill slowly.
朝、学校へ行く途中で急な坂を下りる。
On the way to school in the morning, I go down a steep hill.
その道は車で坂を下りるときに注意が必要だ。
You need to be careful when driving down that road.