cube vs ice cube

cube and ice cube both are nouns.

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

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

Other hyponyms of cube include dice, die.

cube (noun)	ice cube (noun)
a block in the (approximate) shape of a cube	a small cube of artificial ice; used for cooling drinks
any of several tropical American woody plants of the genus Lonchocarpus whose roots are used locally as a fish poison and commercially as a source of rotenone
the product of three equal terms
a hexahedron with six equal squares as faces
a three-dimensional shape with six square or rectangular sides

cube (verb)	ice cube (verb)
raise to the third power
cut into cubes