yet another name for sexual intercourse, derived from the British word for Boloney (Polony) which sounds like 'Pony' British Polony is a curled red cooked meat sausage available from the butchers. Pony Trekking- a popular equestrian activity.
On observing a saddle sore woman at a show jumping event:
man 1:"look at her, she can hardly walk'
man 2 :'I bet she spent the whole night polony trekking'