plug away vs hang on

plug away and hang on both are verbs.

Word	Noun	Adjective	Verb	Adverb
plug away	No	No	Yes	No
hang on	No	No	Yes	No

As verbs, hang on is a hypernym of plug away; that is, hang on is a word with a broader meaning than plug away:

Other hypernyms of plug away include hang in, hold on, persevere, persist.

plug away (verb)	hang on (verb)
persist in working hard	be persistent, refuse to stop
work doggedly or persistently	hold the phone line open
	fix to; attach