wait vs hold the line

wait is a noun but hold the line is not a noun.

Word	Noun	Adjective	Verb	Adverb
wait	Yes	No	Yes	No
hold the line	No	No	Yes	No

As verbs, hold the line is a hyponym of wait; that is, hold the line is a word with a more specific, narrower meaning than wait:

Other hyponyms of wait include expect, look forward, look to, hang on, hold on, anticipate, look for, look to.

wait (noun)	hold the line (noun)
the act of waiting (remaining inactive in one place while expecting something)
time during which some action is awaited

wait (verb)	hold the line (verb)
look forward to the probable occurrence of	hold the phone line open
serve as a waiter or waitress in a restaurant	hold the line on prices; keep the price of something constant
stay in one place and anticipate or expect something
wait before acting