steal vs gain ground

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

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

As verbs, gain ground is a hypernym of steal; that is, gain ground is a word with a broader meaning than steal:

Other hypernyms of steal include advance, gain, get ahead, make headway, pull ahead, win.

steal (noun)	gain ground (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

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