stimulation vs sexual activity

stimulation and sexual activity both are nouns.

Word	Noun	Adjective	Verb	Adverb
stimulation	Yes	No	No	No
sexual activity	Yes	No	No	No

As nouns, sexual activity is a hypernym of stimulation; that is, sexual activity is a word with a broader meaning than stimulation:

Other hypernyms of stimulation include sex, sex activity, sexual practice.

stimulation (noun)	sexual activity (noun)
the act of arousing an organism to action	activities associated with sexual intercourse
mutual sexual fondling prior to sexual intercourse
any stimulating information or event; acts to arouse action
(physiology) the effect of a stimulus (on nerves or organs etc.)