The man had approached the victim who had been walking her dog in the park near Heather Avenue, Dogsthorpe, between 1pm and 2pm on Monday, October 28th.
He spoke to her before exposing himself.
He is described as white, 30 to 45, 5'6'', heavily built with thick dark greasy hair. He had grey-flecked stubble and was wearing a ribbed jumper and combat trousers.
He was also riding a mountain bike.
PC Tina Walsh said: "I would urge anyone who saw this man in the area at the time of the incident, or who recognises the description, to call police."
Anyone with any information should call PC Walsh on 101 or Crimestoppers, anonymously, on 0800 555 111.
google.com/+JulianBray 01733 345581 ## RSS feed: http://feeds.feedburner.com/ParkFarmNeighbourhoodNewsTel01733345581PeterboroughcambridgeshireUk POLICE 101. Emergency 999. Crimestoppers 0800 555 111.