depth bomb vs depth charge

depth bomb and depth charge both are nouns.

Word	Noun	Adjective	Verb	Adverb
depth bomb	Yes	No	No	No
depth charge	Yes	No	No	No

As nouns, depth bomb and depth charge are synonyms defined as:

depth bomb and depth charge: a bomb that explodes at a preset depth under water; antisubmarine device

depth bomb (noun)	depth charge (noun)
a bomb that explodes at a preset depth under water; antisubmarine device	a bomb that explodes at a preset depth under water; antisubmarine device