downhill

(noun) the downward slope of a hill.

(noun) a ski race down a trail.

(adj) sloping down rather steeply. Synonyms: declivitous, downward-sloping.

(adv) toward a lower or inferior state. Example: "Your performance has been going downhill for a long time now."

(adv) toward the bottom of a hill. Example: "Running downhill, he gained a lot of speed."