parcel bomb vs letter bomb

parcel bomb and letter bomb both are nouns.

Word	Noun	Adjective	Verb	Adverb
parcel bomb	Yes	No	No	No
letter bomb	Yes	No	Yes	No

As nouns, parcel bomb and letter bomb are synonyms defined as:

parcel bomb and letter bomb: a thin explosive device inside an envelope or package and detonated when opened

Other synonyms of parcel bomb include package bomb.

parcel bomb (noun)	letter bomb (noun)
a thin explosive device inside an envelope or package and detonated when opened	a thin explosive device inside an envelope or package and detonated when opened

parcel bomb (verb)	letter bomb (verb)
	send an explosive to