ECM vs electronic countermeasures

ECM and electronic countermeasures both are nouns.

Word	Noun	Adjective	Verb	Adverb
ECM	Yes	No	No	No
electronic countermeasures	Yes	No	No	No

As nouns, ECM and electronic countermeasures are synonyms defined as:

ECM and electronic countermeasures: electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum

ECM (noun)	electronic countermeasures (noun)
electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum	electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum