A "pineapple couple" refers to a pair of partners who are involved in the swinging lifestyle, which means they are interested in consensual partner- swapping or non-monogamous sexual activities with other couples. The pineapple, especially when displayed upside-down, is a well-known symbol used by swingers to subtly identify themselves to others with similar interests. This symbol can appear on clothing, accessories, luggage, or even as an actual pineapple placed upside-down in a shopping cart or on a cruise ship cabin door. It serves as a discreet signal to indicate openness to swinging or attending swinger parties

. In summary, a "pineapple couple" is a couple who uses the pineapple symbol to communicate their participation in or interest in the swinging lifestyle.