ice vs pack ice

ice and pack ice both are nouns.

Word	Noun	Adjective	Verb	Adverb
ice	Yes	No	Yes	No
pack ice	Yes	No	No	No

As nouns, pack ice is a hyponym of ice; that is, pack ice is a word with a more specific, narrower meaning than ice:

Other hyponyms of ice include drift ice, icefall, neve, ice pack, ice shelf, shelf ice.

ice (noun)	pack ice (noun)
a rink with a floor of ice for ice hockey or ice skating	a large expanse of floating ice
an amphetamine derivative (trade name Methedrine) used in the form of a crystalline hydrochloride; used as a stimulant to the nervous system and as an appetite suppressant
a frozen dessert with fruit flavoring (especially one containing no milk)
a flavored sugar topping used to coat and decorate cakes
the frozen part of a body of water
diamonds
water frozen in the solid state