If a woman starts stroking a man's penis and he assumes she wants to have PIV sex and does so without her expressing through actions or words that this is what she's hoping for as well, that's rape. If she does nothing because she's too surprised by his actions or afraid, that's still rape because she's not consenting.

Stroking a man's penis does not indicate without a doubt that the person doing it wants that penis in their body, it indicates that they want to stroke the penis.