hold on vs harbor

hold on is not a noun while harbor is a noun.

Word	Noun	Adjective	Verb	Adverb
hold on	No	No	Yes	No
harbor	Yes	No	Yes	No

As verbs, harbor is a hyponym of hold on; that is, harbor is a word with a more specific, narrower meaning than hold on:

hold on (noun)	harbor (noun)
	a place of refuge and comfort and security
	a sheltered port where ships can take on or discharge cargo

hold on (verb)	harbor (verb)
be persistent, refuse to stop	maintain (a theory, thoughts, or feelings)
stop and wait, as if awaiting further instructions or developments	hold back a thought or feeling about
hold the phone line open	keep in one's possession; of animals
hold firmly	secretly shelter (as of fugitives or criminals)
retain possession of