peninsula vs solid ground

peninsula and solid ground both are nouns.

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

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

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

peninsula (noun)	solid ground (noun)
a large mass of land projecting into a body of water	the solid part of the earth's surface