adverb
toward the bottom of a hill or mountain
toward a worse state
adjective
going or sloping down toward the bottom of a hill or mountain
not used before a noun
not difficult :easy to do, deal with, etc.
becoming worse or less successful
always used before a noun :relating to or used in a kind of skiing that is done down a mountain or hill instead of over the countryside
noun
plural -hills
[count] :a downhill skiing race - usually singular
US