adv., adj., & n.
adv. in a descending direction, esp. towards the bottom of an incline.
adj. 1 sloping down, descending. 2 declining; deteriorating.
n. 1 Skiing a downhill race. 2 a downward slope. 3 a decline. go downhill colloq. decline, deteriorate (in health, state of repair, moral state, etc.).