forest vs solid ground

forest and solid ground both are nouns.

Word	Noun	Adjective	Verb	Adverb
forest	Yes	No	Yes	No
solid ground	Yes	No	No	No

As nouns, solid ground is a hypernym of forest; that is, solid ground is a word with a broader meaning than forest:

Other hypernyms of forest include biome, dry land, earth, ground, land, terra firma.

forest (noun)	solid ground (noun)
the trees and other plants in a large densely wooded area	the solid part of the earth's surface
land that is covered with trees and shrubs

forest (verb)	solid ground (verb)
establish a forest on previously unforested land