junk heap vs junk pile

junk heap and junk pile both are nouns.

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

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

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

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