Definition from Wiktionary, the free dictionary
foreskin (plural foreskins)
- The retractable fold of skin encompassing the most nerve-dense tissue in the human male, which naturally covers and protects the head of the penis.
- And the uncircumcised man child whose flesh of his foreskin is not circumcised, that soul shall be cut off from his people; he hath broken my covenant. — Genesis 17:14, the Christian Bible.
- In primates, the foreskin is present in the genitalia of both sexes and likely has been present for millions of years of evolution. 
- "The foreskin has two main functions. Firstly it exists to protect the glans penis. Secondly the foreskin is a primary sensory part of the penis, containing some of the most sensitive areas of the penis." - The Royal Australasian College of Physicians
- The female clitoral hood is homologous with the foreskin.
fold of skin — see prepuce