ice pack vs pack ice

ice pack and pack ice both are nouns.

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

As nouns, ice pack and pack ice are synonyms defined as:

ice pack (noun)	pack ice (noun)
a waterproof bag filled with ice: applied to the body (especially the head) to cool or reduce swelling	a large expanse of floating ice
a large expanse of floating ice