rubbish heap vs junk heap

rubbish heap and junk heap both are nouns.

Word	Noun	Adjective	Verb	Adverb
rubbish heap	Yes	No	No	No
junk heap	Yes	No	No	No

As nouns, rubbish heap and junk heap are synonyms defined as:

rubbish heap and junk heap: an accumulation of refuse and discarded matter

Other synonyms of rubbish heap include garbage heap, junk pile, refuse heap, scrapheap, trash heap, trash pile.

rubbish heap (noun)	junk heap (noun)
an accumulation of refuse and discarded matter	an accumulation of refuse and discarded matter