What is Downhill ?
Downhill is (adv) 1. towards the bottom of a hill The road goes downhill for a while and then crosses the river. 2. to go downhill to get worse The economy is going downhill. The business started to go downhill when the old manager left. (adj) downhill (skiing) competition a skiing competition which involves going down a hill as fast as you can, more or less in a straight line
source: Easier English, Student Dictionary Upper Intermediate Level