firm, hard, solid
muddy, soft
damp, wet
dry, dusty
cold, frozen
dirt (AmE)
concrete, stone (both esp. AmE)
snow-covered, snowy
sandy
fertile (often figurative)
The fall of the old regime provided fertile ground for opportunism.

fall to, hit, strike, touch
The helicopter burst into flames when it hit the ground.

reach
Her feet don't reach the ground when she sits down.

get off, leave
The plane was so overloaded it couldn't leave the ground.
His plan is too costly to ever get off the ground. (figurative)

cover, litter
the broken branches which littered the ground

kick, paw, pound
The horse pawed the ground impatiently.

scan, search
Her eyes searched the ground.

shake
Thunder shook the ground.

level
The window is just above ground level.

forces, troops

the ground beneath sb's feet

above ground, below ground
The roots may spread as far below ground as does the foliage above ground.

in the ground
a hole in the ground

on the ground
He sat down on the ground.

under the ground
The tunnel goes deep under the ground.

high, low
The town stands on high ground and is not prone to flooding.

open
difficult, rocky, rough, stony, uneven
bare, barren
flat, level
marshy
hallowed, holy, sacred
He stood on the hallowed ground of Yankee Stadium. (figurative)

patch, piece
We found a patch of open ground in the middle of the woods.

burial
dumping
The river has become a dumping ground for industrial waste.
Landfill sites provide a dumping ground for old mattresses, broken chairs as well as household waste.

camp (AmE), parade
battle
breeding, feeding, nesting, spawning, wintering
The estuary is a breeding ground for birds and marine life.
Hospitals are breeding grounds for bacteria.
Poverty is a breeding ground for terrorism. (figurative)

fishing, hunting
staging (esp. AmE)
meeting

at a/the ground, in a/the ground
all the graves in the burial ground

cricket, football, rugby, etc.
practice, recreation, sports, training
away, home

at a/the ground
I'll meet you at the football ground.

inside a/the ground
The atmosphere inside the ground was electric.

extensive, large
castle, hospital, palace, school, etc.
surrounding

be set in, have
The palace is set in extensive grounds.

cross, enter, walk

in the grounds (of) (esp. BrE)
She lived in the grounds of the castle.

on the grounds (of) (AmE)
The doctor's office is on the grounds of the hospital.

familiar, home, old
I was on more familiar ground now that we were talking about our own system.
I apologize if I'm going over old ground.

firm, solid
dangerous, rocky, shaky
Legally, we're on very shaky ground (= our actions may not be legal).
Both relationships hit rocky ground.

safe
common
Both parties in the debate shared some common ground.

middle
a search for middle ground between the two sides

neutral

cover, go over, tread
Several researchers have published articles covering this ground.
We just seem to be going over the same ground that we covered last year.

on … ground
He knew he was on dangerous ground talking about money.

break new ground
Her architectural designs have broken new ground.

hold your ground, stand your ground
She held her ground in the debate.

the moral high ground
I was angry with his blatant attempt to take the moral high ground.

shift your ground
Each time he seemed to be losing the argument, he just shifted his ground.

good, reasonable, strong, sufficient
legitimate, valid
ethical, humanitarian, moral
economic, legal, political, etc.

have
The police had reasonable grounds for arresting her.

be, give (sb)
His evasiveness gave grounds for suspicion.

on … grounds
Permission to open a mine was denied on environmental grounds.

on the grounds of
He resigned on the grounds of ill health.

ground for
Drunkenness at work was sufficient grounds for instant dismissal.