electronic jamming vs ECM

electronic jamming and ECM both are nouns.

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

As nouns, ECM is a hypernym of electronic jamming; that is, ECM is a word with a broader meaning than electronic jamming:

electronic jamming: deliberate radiation or reflection of electromagnetic energy for the purpose of disrupting enemy use of electronic devices or systems
ECM: electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum

Other hypernyms of electronic jamming include electronic countermeasures.

electronic jamming (noun)	ECM (noun)
deliberate radiation or reflection of electromagnetic energy for the purpose of disrupting enemy use of electronic devices or systems	electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum