halloo vs scream

halloo and scream both are nouns.

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

As verbs, scream is a hypernym of halloo; that is, scream is a word with a broader meaning than halloo:

Other hypernyms of halloo include call, cry, holler, hollo, shout, shout out, squall, yell.

halloo (noun)	scream (noun)
a shout to attract attention	sharp piercing cry
	a joke that seems extremely funny
	a high-pitched noise resembling a human cry

halloo (verb)	scream (verb)
shout `halloo', as when greeting someone or attracting attention	utter a sudden loud cry
urge on with shouts	utter or declare in a very loud voice
	make a loud, piercing sound