detumescence
/ˌdiːtjʊˈmɛs(ə)ns
/noun [mass noun]
The process of subsiding from a state of tension, swelling, or (especially) sexual arousal.
Derivatives
detumesce
detumescent
Origin
Late 17th century: from Latin detumescere, from de- 'down, away'+ tumescere 'to swell'.