noun, feminine/mas.tyʁ.ba.sjɔ̃ my.tɥɛl/plural: masturbations mutuelles
masturbation mutuelle is feminine in French.
mutual masturbation
“Parmi les hommes homosexuelles la fellation et la masturbation mutuelle seraient des pratiques plus courantes que le sodomie.” — Among homosexual men, fellatio and mutual masturbation are more common than anal sex.