Smegma

Mary told Tom to wash the smegma off his penis the next time he wanted a blowjob.

There was smegma under his foreskin.

It's common sense to keep your foreskin constantly retracted so that smegma is unable to accumulate.

I saw Mrs St Cloud wander happily through the flower-filled streets, her belly smeared with smegma, breasts bruised by the hands of boys.