A nicely shaped, and usually freshly shaved vulva, typically characterized by large labia majora (outer lips) and small, if not invisible, labia minora (inner lips). A peach features absolutely no roast beef, and is considered by many men to be the ideal vulva for a woman.
Did you see her vagina? It was perfect! What a peach!
Urban or Freudian allusion to a vulva. The juiciness, soft hair, and shape of the fruit obviously resemble the female vulva. Biting into a peach, with the consequent explosion of juices, is often invoked as a Freudian exposition of male (or female) libido.
"Do I dare eat to a peach..."
T.S. Elliot - The Love Song of J. Alfred Prufrock