gain ground vs steal

gain ground is not a noun while steal is a noun.

Word	Noun	Adjective	Verb	Adverb
gain ground	No	No	Yes	No
steal	Yes	No	Yes	No

As verbs, steal is a hyponym of gain ground; that is, steal is a word with a more specific, narrower meaning than gain ground:

Other hyponyms of gain ground include rack up, score, tally.

gain ground (noun)	steal (noun)
	a stolen base; an instance in which a base runner advances safely during the delivery of a pitch (without the help of a hit or walk or passed ball or wild pitch)
	an advantageous purchase

gain ground (verb)	steal (verb)
obtain advantages, such as points, etc.	steal a base
	move stealthily
	take without the owner's consent