halloo vs outcry

halloo and outcry both are nouns.

Word	Noun	Adjective	Verb	Adverb
halloo	Yes	No	Yes	No
outcry	Yes	No	Yes	No

As nouns, outcry is a hypernym of halloo; that is, outcry is a word with a broader meaning than halloo:

Other hypernyms of halloo include call, cry, shout, vociferation, yell.

halloo (noun)	outcry (noun)
a shout to attract attention	a loud utterance; often in protest or opposition

halloo (verb)	outcry (verb)
shout `halloo', as when greeting someone or attracting attention	utter aloud; often with surprise, horror, or joy
urge on with shouts	shout louder than