n. A licensed premises located above the Mosman Rowing Club, in the affluent northern suburb of Mosman in Sydney, Australia. It is a famous 'pick-up' joint frequented by divorced females aged over 45. The women patrons are usually over-weight, well-worn (ugly and used-up), have dyed blond hair and wear inappropriately tight fitting clothing (borrowed from their 24 year old daughter's wardrobe). The male patrons are all baby boomer types over 50 years old, sporting a grey moustache (or other grey facial hair) and have a massive 'beer-gut' (fat stomachs). These sad creatures usually consume large amounts of alcohol before leaving with someone they have never met for a 5 minute session of 'grey-sex'.
Bill went to the Mosman Rowers to grab a granny. He needed 5 minutes of poor quality 'grey-sex'.