flasher vs streaker

flasher and streaker both are nouns.

Word	Noun	Adjective	Verb	Adverb
flasher	Yes	No	No	No
streaker	Yes	No	No	No

As nouns, streaker is a hyponym of flasher; that is, streaker is a word with a more specific, narrower meaning than flasher:

flasher: someone with a compulsive desire to expose the genitals
streaker: someone who takes off all their clothes and runs naked through a public place

flasher (noun)	streaker (noun)
an electrical device that automatically turns a lamp on and off (as for an advertising display)	someone who takes off all their clothes and runs naked through a public place
a light that flashes on and off; used as a signal or to send messages
someone with a compulsive desire to expose the genitals