winter break vs holiday

winter break and holiday both are nouns.

Word	Noun	Adjective	Verb	Adverb
winter break	Yes	No	No	No
holiday	Yes	No	Yes	No

As nouns, holiday is a hypernym of winter break; that is, holiday is a word with a broader meaning than winter break:

winter break: A school holiday in winter, the date and duration of which depends on the country.
holiday: leisure time away from work devoted to rest or pleasure

Other hypernyms of winter break include vacation.

winter break (noun)	holiday (noun)
A school holiday in winter, the date and duration of which depends on the country.	leisure time away from work devoted to rest or pleasure
	a day on which work is suspended by law or custom

winter break (verb)	holiday (verb)
	spend or take a vacation