lip-strap

plural lip-straps

1. A small strap with a buckle running between the cheeks of a bit, to prevent the horse from biting on the cheek of the bit in its mouth.

   He was not a horsey man, but he liked people to believe he had been one once; and he wove fantastic stories of the hunting-bridle to which this particular lip-strap had belonged.

   1888, Rudyard Kipling, “Watches of the Night”, in Plain Tales from the Hills, Folio, published 2005, page 59