pipe up vs yell

pipe up is not a noun while yell is a noun.

Word	Noun	Adjective	Verb	Adverb
pipe up	No	No	Yes	No
yell	Yes	No	Yes	No

As verbs, yell is a hypernym of pipe up; that is, yell is a word with a broader meaning than pipe up:

Other hypernyms of pipe up include call, cry, holler, hollo, scream, shout, shout out, squall.

pipe up (noun)	yell (noun)
	a loud utterance; often in protest or opposition
	a loud utterance of emotion (especially when inarticulate)

pipe up (verb)	yell (verb)
begin to play or sing	utter or declare in a very loud voice
utter a shrill cry	utter a sudden loud cry