precipitous, severe, sheer, steep | gentle, gradual, slight | long, short | downhill, downward | uphill, upward | higher, upper
There was snow on the higher slopes of the mountain.

lower | northern, north-facing, etc.
The vineyards on the south-facing slopes get more sunshine.

open | forested, grassy, icy, rocky, scree, smooth, snow-covered/snowy, wooded | mountain | dry, nursery, ski
dry-slope skiing Some tourists were having a skiing lesson on the nursery slope.

negative, positive
The unemployment-income curve on the graph has a negative slope.

slippery
(figurative) Once he''d tried that first cigarette, he was on the slippery slope to being a smoker.

ascend, clamber up, climb (up)
We clambered up the steep, rocky slope.

descend | have
The football pitch has a slope of about one metre.

lead (up/down) to sth
a slope leading down to the river

fall, rise
The lower slopes rise quite gently.

steepen | flatten, level off

down a/the ~
I scrambled down the icy slope.

on a/the ~
We camped on an open mountain slope.

up a/the ~
There were more skiers further up the slope.

the angle of slope
the angle of slope of the sides of the pyramid

the bottom/foot/top of a slope

steeply
The ground slopes away steeply at the back of the house.

gently, slightly | away, down, downwards, up, upwards

to
The field slopes down to a small river.

towards