An upside down pineapple in your grocery cart, or as a bumper sticker, or an upside down door knocker indicates the person is into swinging. – WTF Fun Facts
Source: https://onairwithryan.iheart.com/featured/ryan-seacrest/content/2019-01-11-do-you-know-what-an-upside-down-pineapple-means-tanya-tests-it-out-/
