flashover vs electric discharge

flashover and electric discharge both are nouns.

Word	Noun	Adjective	Verb	Adverb
flashover	Yes	No	No	No
electric discharge	Yes	No	No	No

As nouns, electric discharge is a hypernym of flashover; that is, electric discharge is a word with a broader meaning than flashover:

flashover: an unintended electric discharge (as over or around an insulator)
electric discharge: electrical conduction through a gas in an applied electric field

Other hypernyms of flashover include arc, discharge, electric arc, spark.

flashover (noun)	electric discharge (noun)
an unintended electric discharge (as over or around an insulator)	electrical conduction through a gas in an applied electric field