(1) Signboard consisting of two hinged boards that hang front and back from the shoulders of a walker and are used to display advertisements
WiktionaryText
Noun
A person-sized, wearable billboard or advertisement consisting of two printed boards strung together so that they hang over the shoulders, thereby sandwiching the wearer.
Verb
sandwich board, sandwich boarding
to advertise or campaign using a sandwich board; to wear a sandwich board.
